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We are pleased to announce the Higgs 2022 Conference that will take place in the on-site format.
The conference will focus on new experimental and theoretical results on the Higgs boson.
Latest measurement of the Higgs boson properties and recent theoretical developments in the Higgs boson sector, in the Standard Model and in physics Beyond the Standard Model will be presented and discussed at the Conference.
Contributions will be organised in several parallel and plenary sessions.
During the the Conference, the ten years anniversary of Higgs boson discovery will be celebrated with a round table opened to the general public.
The round table, in Italian, will be broadcasted here.
The conference is planned to be kept in hybrid format with a substantial in-person participation, in compliance with the relevant COVID-19 regulations at the time of the meeting. We have more than 180 registered participants. To ensure a smooth and stable running of the event, access via zoom to the conference is given with priority to the few speakers who have not been able to come to Pisa in person. To allow a broader participation, we will have two live broadcasts via CERN:
The videos of the presentations will be available on indico with a delay of a few days.
COVID traveler information to enter in Italy can be found here
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The mass of the Higgs boson can be measured in the Higgs to four leptons and Higgs to two photons decay channels, where the excellent mass resolution can be used to reconstruct the Higgs boson invariant mass. The same decays can be used to measure the Higgs boson natural width, either by exploiting the offshell Higgs contribution to the four leptons and two leptons plus two neutrinos production at high mass, or the interference of the Higgs to diphotons decay with the diphotons continuous production. This talk presents the most recent measurements of Higgs boson mass and width by the ATLAS experiment exploiting the Higgs boson decays into two photons or four leptons, using the full Run 2 dataset of pp collisions collected at 13 TeV at the LHC. This talk also reviews recent improvements of the muon reconstruction, identification and momentum calibration in ATLAS, crucial to the measurement of the Higgs boson mass in the four-lepton channel. New analysis techniques are exploited, including multivariate analyses for rejecting background hadrons from prompt muons from the hard interactions, as well as in-situ corrections significantly reducing biases in muon momenta induced by residual detector displacements
The latest measurement of the Higgs mass in the 4l final state at CMS will be presented. The prospects with the HL-LHC on the Higgs mass sensitivity will also be shown.
With the full Run 2 pp collision dataset collected at 13 TeV, very detailed measurements of Higgs boson coupling and kinematical properties can be performed, exploiting a variety of final states and production modes, probing different regions of the phase space with increasing precision. Coupling, fiducial and differential measurements can then be combined to exploit the specific strength of each channel, thus providing the most stringent global measurement of the Higgs properties. This talk presents the latest combination of Higgs boson coupling measurements by the ATLAS experiment, discussing results in term of production modes, branching fractions and Simplified Template Cross Sections, as well as their interpretations in the framework of kappa modifiers to the strength of the various coupling and decay properties; and the latest combination of the Higgs boson fiducial and differential cross sections in various Higgs boson decays, as well as their combination and interpretations in term of constrain of beyond-the-Standard-Model phenomena.
The most recent fiducial differential cross section measurements performed in the $\mathrm{H}\rightarrow{\rm Z}{\rm Z}\rightarrow4\ell$ ($\ell={\rm e},\mu$) decay channel are presented. The results have been obtained using data collected by the CMS experiment, corresponding to an integrated luminosity of 138 fb-1 at a centre of mass energy of 13 TeV. The fiducial cross section is measured with respect to several observables sensitive to the production and decay of the Higgs boson, where the observed results are compared with different theory predictions. A summary of possible interpretations of the obtained results is also presented.
The VBF production mode has the 2nd largest production cross section for Higgs bosons in the SM at the LHC, and provides a way to study the Higgs boson's interactions with vector bosons. In this talk, recent measurements of the VBF Higgs boson production mode at CMS will be discussed. All measurements make use of data collected during Run 2 of the LHC.
Higgs data can provide better constrains on some top quark operators than top data. Since in Higgs observables various SMEFT operators enter, differential Higgs data might prove useful in global fits including those operators. In addition, such analysis could shed light on the chiral structure of the (eventual) heavy new physics beyond the Standard Model.
We calculate the dominant contributions of third generation four-quark operators to Higgs+jet production. They enter via loop corrections
to the (partonic) processes $gg\to gH$, $q\bar{q} \to gH$, $q(\overline{q})g\to q(\bar{q})H$, whose dominant Standard Model amplitude arises at one-loop level. Consequently, the inclusion of NLO ($\mathcal{O}\left(1/\Lambda^2\right)$) contributions to these processes requires a two-loop computation.
Our analysis consists in computing the matrix elements and, subsequently, the (hadronic) cross section via Monte Carlo integration. Finally we perform a fit to put bounds on the considered SMEFT coefficients.
We present an updated global SMEFT analysis in the Higgs and Electroweak sectors with the SFitter framework.
The main result we present is the comparison of the results obtained with a frequentist and with a bayesian approach. The implementation of Bayesian inference in the SFitter framework is one of the main novelties of this work, and it is motivated by its greater scalability to large-dimensional fits and faster numerical convergence, compared to the frequentist likelihood treatment.
Further, we include new measurements for the Full Run II data published in recent years by the LHC experiments. We will stress the importance of a careful uncertainty treatment in this context, particularly of flat theory uncertainties. We will also discuss the impact of high invariant mass measurements on kinematically enhanced operators.
Finally, we enlarge the set of constrained operators to include corrections to the muon Yukawa coupling and to the top chromomagnetic dipole moment.
We present the most recent searches for CP and anomalous couplings (AC) in Higgs boson production and decay. Couplings of the Higgs boson to both vector bosons and fermions will be discussed in various production channels and final states. The results have been performed with data from the full CMS Run 2 dataset, corresponding to an integrated luminosity of 138 fb−1 at a center-of-mass energy of 13 TeV. They significantly improve upon previous constraints. Results in the context of effective field theories (EFT) will also be presented.
In the absence of direct observations of new physics beyond the Standard Model, interpretations of results using Effective Field Theories can be a powerful tool to place near-model-independent constraints on new physics scenarios, or better observe deviations from the Standard Model and have it interpreted in terms of specific new interactions. This talk presents Effective Field Theory interpretations of individual and combined results from the ATLAS experiment, including the combined measurements of the Higgs boson coupling properties.
The electroweak symmetry-breaking sector is one of the most promising and uncharted parts of the Standard Model; but it seems likely that new electroweak physics may be out of reach of the present accelerator effort
and the hope is to observe small deviations from the SM. Given that, Effective Field Theory becomes the logic method to use, and SMEFT has become the standard. However, the most general theory with the known particle content is HEFT, and whether SMEFT suffices should be investigated in future experimental efforts. Building on investigations by other groups that established geometric criteria to distinguish SMEFT from HEFT (useful for theorists examining specific beyond-SM completions), we seek more phenomenological understanding and present an analogous discussion aimed at a broader audience. We discuss various aspects of (multi-) Higgs boson production from longitudinal electroweak gauge bosons
$W_L W_L \to n \times h$ in the TeV region as the necessary information to characterise the Flare function, $\mathcal{F}(h)$, which determines whether SMEFT or HEFT is needed. We also present tree-level amplitudes including contact and exchange channels, as well as a short discussion on accessing F from the statistical limit of many bosons. We discuss the status of the coefficients of the series expansion of $\mathcal{F}(h)$, its validity, whether its complex-h extension can be used to predict or not a tell-tale zero, and how they relate to the dimension-6 and -8 SMEFT
operators in the electroweak sector. We derive a set of new correlations among BSM corrections to the HEFT coefficients that help decide, from experimental data, whether we have a viable SMEFT. This analysis can be
useful for machines beyond the LHC that could address the challenging final state with several Higgs boson.
We analyse the sensitivity to beyond-the-Standard-Model effects of hadron-collider processes involving the interaction of two electroweak (V) and two Higgs (H) bosons, VVHH, with V being either a W or a Z boson.
We examine current experimental results by the CMS collaboration in the context of a dimension-8 extension of the Standard Model in an effective-field-theory formalism. We show that constraints from vector-boson-fusion Higgs-pair production on operators that modify the Standard Model VVHH interactions are already comparable with or more stringent than those quoted in the analysis of vector-boson-scattering final states. We study the modifications of such constraints when introducing unitarity bounds, and investigate the potential of new experimental final states, such as ZHH associated production. Finally, we show perspectives for the high-luminosity phase of the LHC.
This talk will present a measurement of the charge conjugation and parity ($CP$) properties in the Higgs boson interaction with $\tau$ leptons. The Yukawa interaction is generalized with a single mixing angle parameter $\phi_{\tau}$ to describe $CP$-odd interactions between the Higgs boson and $\tau$ leptons. The study is based on a measurement of $CP$-sensitive angular observables defined by the visible decay products of $\tau$ lepton decays, performed using a data sample corresponding to 139 fb$^{-1}$ of proton???proton collisions recorded at a center-of-mass energy of $\sqrt{s}$= 13 TeV with the ATLAS detector at the Large Hadron Collider. Without assuming Standard Model hypothesis for the $H\rightarrow\tau\tau$ signal strength, the mixing angle $\phi_{\tau}$ is measured to be $9 \pm 16^{\circ}$, with an expected value of $0 \pm 28^{\circ}$ at the 68\% confidence level. The pure $CP$-odd hypothesis is disfavoured at 3.4 standard deviations. The results are compatible with the predictions for the Higgs boson in the Standard Model as well as $CP$-violating scenarios.
Recent years have seen an unprecedented development of techniques devoted to identifying jets from the hadronization of heavy flavor quarks. This was made possible by the extensive usage of modern machine learning techniques. In particular, the identification of heavy resonance final states involving a pair of bottom or charm quarks largely benefited from these developments. In addition, boosted topologies have also been explored in the di-tau final state. For this case dedicated tau reconstruction techniques were developed to resolve tau leptons stemming from the decay of a highly boosted Higgs boson. This talk presents a compendium of the most recent CMS analyses searching for Higgs bosons decaying into bottom or charm quark-antiquark pairs, or pairs of tau leptons, in the boosted regime by exploiting the main production modes: gluon-fusion (ggH), associated production (VH), and vector boson fusion (VBF). The techniques employed for flavor tagging will in particular be discussed. The analyses have been carried out exploiting the full Run-2 dataset collected by the CMS experiment at sqrt(s)=13 TeV.
This talk will present the latest CMS results on the measurement of Higgs boson production with H->bb decays. It will consider the Higgs boson production via gluon fusion in the boosted topology (ggF Hbb), via vector boson fusion (VBF Hbb), in association with a vector boson (VH Hbb), and with a top quark pair (ttHbb). In addition, the talk will discuss the latest results of the search for the non-resonant HH production in the 4b final state with full Run 2 LHC data.
The measurement of the H->bbbar decay rate by ATLAS and CMS offers an opportunity to test the scale evolution or "running" of the bottom quark mass. With an excellent mass sensitivity, reduced dependence on alpha_s and a clearly identifiable scale, the Higgs decay process is the ideal laboratory to extract a high-scale quark mass. The mass at the scale given by the Higgs boson mass, mb(mH) is determined to be 2.6 +/- 0.3 GeV. Combining this new measurement with the determination of mb(mb) from low-energy data and mb(mZ) from LEP and SLD measurements at the Z-pole, we revisit the scale evolution of the bottom quark mass, finding an unambiguous confirmation of this SM prediction. The result from PRL128 (2021) is updated with the latest results by ATLAS and CMS and projections of the future precision at the HL-LHC and a future Higgs/top/EW factory are presented.
Many physics analyses using the CMS detector at the LHC require accurate, high resolution electron and photon energy measurements. Excellent energy resolution is crucial for studies of Higgs boson decays with electromagnetic particles in the final state, as well as searches for very high mass resonances decaying to energetic photons or electrons. The CMS electromagnetic calorimeter (ECAL) is a fundamental component of these analyses, and its energy resolution is crucial for the Higgs boson mass measurement in the H->ZZ->4l and H->gg channels.
The energy response of the calorimeter has been precisely calibrated exploiting the full Run 2 (2015-18) dataset, and has been used for the legacy reprocessing of these data. A dedicated calibration of each detector channel has been performed. This talk will summarize the improved ECAL performance that has been achieved, and will describe how this impacts on the sensitivity of the Higgs mass measurement in the H->ZZ->4l and H->gg channels. The calibration plans currently being developed to achieve and maintain the optimum ECAL performance during LHC Run 3 (2022-25) will also be discussed. A new system has been developed to automatically execute the calibration workflows on a daily basis during data taking in Run 3. This new development aims to reduce the time needed to provide the best possible performance for physics analyses by one order of magnitude. The general structure of the system will be presented, along with results from the first year of operation in 2022.
Nearly all physics analyses at CMS rely on the precise reconstruction of particles from their signatures observed in the experiment’s calorimeters. This involves both energy reconstruction, including the recovery of energy lost in gaps and cracks within the detector volumes, and particle identification. These tasks have traditionally been performed by classical algorithms and BDT regressions, both of which rely on human-engineered high-level quantities.
Bypassing human “feature engineering”, and instead training deep learning algorithms on low-level signals, has the potential to recover lost information and improve the overall reconstruction performance. We have developed novel algorithms for particle reconstruction in the CMS calorimeters based on graph neural networks (GNNs) which allow us to represent the energy deposits recorded in the calorimeter directly in our models. We have also developed end-to-end mass regression techniques using convolutional neural networks (CNNs), that allow us to reconstruct merged photons from highly Lorentz-boosted decays, such as H->aa->4g, using low-level detector information.
In this work we will show the performance of our machine learning architectures in energy clustering, energy estimation and mass regression in the CMS Electromagnetic Calorimeter (ECAL). We will demonstrate the impact of these techniques in terms of improved energy resolution, significantly improved mass resolution for merged photon decays, and better resilience to effects such as detector gaps, early showering upstream of the calorimeter, and pileup, with respect to the previous state-of-the-art approaches.
Diboson production processes provide good targets for precision measurements at present and future hadronic colliders. We consider $Vh$ production, focusing on the $h \to b\bar b$ decay channel, whose sizeable cross section makes it easily accessible at the LHC. We perform an improved analysis combining the 0-, 1- and 2-lepton channels with a scale-invariant $b$-tagging algorithm that allows us to exploit events with either a boosted Higgs or resolved $b$-jets. This procedure offers a competitive sensitivity to 4 dimension-6 SMEFT operators, $\mathcal{O}_{\varphi q}^{(3)}$, $\mathcal{O}_{\varphi q}^{(1)}$, $\mathcal{O}_{\varphi u}$ and $\mathcal{O}_{\varphi d}$.
At FCC-hh, the $h \to b \bar b$ decay channel is competitive with the cleaner $h\to \gamma\gamma$ channel, provided systematic uncertainties can be kept under good control. In this context, we show that a rapidity binning can significantly reduce correlations, improving the sensitivity to $\mathcal{O}_{\varphi q}^{(1)}$ and $\mathcal{O}_{\varphi u}$.
Finally, we assess the impact of the $Vh$ production channel on aTGC measurements, comparing with the determination at lepton colliders.
Based mostly on 2207.YYZZZ (to be published soon) and partially on 2011.13941 and 2004.06122.
The High-Luminosity LHC (HL-LHC) era will herald significant increases in both the instantaneous luminosity and the number of interactions per bunch crossing. To cope with these significantly more complex conditions, detector upgrades are planned to maintain and surpass the current physics performance. The replacement of the current Inner Detector with a new all-silicon Inner Tracker (ITk) is one of the key upgrades planned for the ATLAS detector. The ITk upgrade provides excellent tracking performance, which will enhance other reconstruction algorithms dependent upon tracking, and ultimately the physics reach of the experiment. In particular, the identification of jets originating from heavy flavour hadrons, known as flavour tagging, is heavily reliant upon tracking and is ideally placed to benefit from the detector upgrade. The performance of recent state-of-the-art flavour tagging algorithms [1,2] applied to the upgraded ATLAS detector was previously presented, which achieved significant performance enhancements to the benefit of several physics analyses. However, new algorithmic developments could further benefit from the HL-LHC detector upgrades to provide additional enhancements in the performance. This talk will survey recent algorithmic developments in the ATLAS flavour tagging community, including algorithms based on deep sets and graph neural networks, and compare their performance with the previous algorithms in the context of HL-LHC upgrades such as the ITk.
The FCC-ee offers powerful opportunities to determine the Higgs boson parameters, exploiting over 106 e+e−→ZH events and almost 105 WW→H events at centre-of-mass energies around 240 and 365 GeV. This essay spotlights the important measurements of the ZH production cross section and of the Higgs boson mass. The measurement of the total ZH cross section is an essential input to the absolute determination of the HZZ coupling -- a "standard candle" that can be used by all other measurements, including those made at hadron colliders -- at the per-mil level. A combination of the measured cross sections at the two different centre-of-mass energies further provides the first evidence for the trilinear Higgs self-coupling, and possibly its first observation if the cross-section measurement can be made accurate enough. The determination of the Higgs boson mass with a precision significantly better than the Higgs boson width (4.1 MeV in the Standard Model) is a prerequisite to either constrain or measure the electron Yukawa coupling via direct e+e−→H production at √s=125 GeV. Approaching the statistical limit of 0.1% and O(1) MeV on the ZH cross section and the Higgs boson mass, respectively, sets highly demanding requirements on accelerator operation (ZH threshold scan, centre-of-mass energy measurement), detector design (lepton momentum resolution, hadronic final state reconstruction performance), theoretical calculations, and analysis techniques (efficiency and purity optimization with modern tools, constrained kinematic fits, control of systematic uncertainties).
With technically mature design and well understood physics program, ILC is realistic option for realization of a Higgs factory. With a unique physics reach of a linear collider, ILC meaningfully complement projections for HL-LHC. Energy staged data collection, employment of beam polarization and capability to reach a TeV center-of-mass energy enable unique precision to probe BSM models above the discovery limit as well as to measure the Higgs self-coupling. These and other ILC studies in the Higgs sector will be discussed.
In the years 1922-1926 Enrico Fermi, then in his early twenties, was scientifically active in Pisa, Gottingen, Leiden and Florence. Apart from his experimental thesis on X rays, most of his research activity was purely theoretical, and covered a wide spectrum of issues, from general relativity (Fermi coordinates, electromagnetic mass) to statistical mechanics (Fermi statistics), from atomic physics to collision theory (method of virtual photons) and to the newborn wave mechanics. We briefly review the main results he obtained in that period, stressing their originality and permanent relevance.
LHCb is a spectrometer that covers the forward region of proton-proton collisions, in the pseudo rapidity range from 2 to 5. Thanks to the relatively background-free events in the high mass region, the precise reconstruction, and the trigger system with low energy thresholds, LHCb is the ideal place to search for (exotic) Higgs decays in a complementary space with respect to ATLAS and CMS. In this talk, the latest searches on BSM Higgs decays performed at LHCb will be presented, and the prospects for future LHC data-taking periods will be given. Moreover the possibility of observing the Standard Model H->bb and H->cc decays at LHCb in the future LHCb upgrades will be discussed.
With the discovery of the Higgs boson at the CERN Large Hadron Collider (LHC), the particle spectrum of the Standard Model (SM) is complete. The next target at the energy frontier will be to study the Higgs properties and to search for the next scale beyond the SM. Experimentally, the $H\to c \bar{c}$ channel would be extremely difficult to dig out because of both the weak Yukawa coupling and the daunting SM di-jet background. We propose to test the charm-quark Yukawa coupling at the LHC and future hadron colliders with the Higgs boson decay to $J/\psi$ via the charm-quark fragmentation. Using the non-relativistic quantum chromodynamics (NRQCD), we study the Higgs decay channel $ H \to c \ \bar{c} + J/\psi $(or $ \eta_c $), where both the color-singlet and color-octet contributions are considered. The decay rates are governed by the charm-quark Yukawa coupling, unlike the decay $H\to J/\psi + \gamma$, which is dominated by the $\gamma^*$-$J/\psi$ mixing. Our result opens another door to improve determinations at the LHC of the Higgs Yukawa couplings: the final state from this decay mode is quite distinctive with $J/\psi\to e^+e^-,\, \mu^+\mu^-$ and the branching fraction is logarithmically enhanced by the charm-quark fragmentation mechanism.
The most recent direct searches for the H→cc process by the CMS Collaboration will be presented. The results are obtained using the full Run 2 LHC data collected in proton-proton collisions at a center of mass energy of 13 TeV, targeting the associated production of the Higgs boson with a Vector boson (W or Z boson) and, for the first time, the gluon fusion production mechanism. To fully exploit the Higgs decay topology in the different regimes of the Higgs boson transverse momentum, two strategies have been adopted for the Higgs candidate reconstruction; Either as two well-separated and individually resolved small-radius jets or as a single large-radius jet, which is more relevant for Higgs bosons with higher momentum. The analyses build on novel machine learning-based algorithms for charm quark(s) identification, and jet and mass regression. The analyses are validated by observing the VZ, Z→cc, and the Drell-Yan, Z→cc processes for the first time at a hadron collider experiment. The results represent the world’s most stringent constraints on Higgs-charm Yukawa coupling.
Testing the Yukawa couplings of the Higgs boson to fermions is essential to understand the origin of their masses, and studies are made by exploring the properties of the Higgs boson decays to quark pairs. The talk presents various measurements of the Higgs boson decays to two bottom quarks and searches for Higgs boson decays to two charm quarks by the ATLAS experiment using the full Run 2 dataset of pp collisions collected at 13 TeV at the LHC, as well as their combination and interpretation.
I present the computation of the two-loop helicity amplitudes for Higgs boson production in association with a bottom quark pair. This work is of relevance to the precision studies of the bottom-quark Yukawa coupling, such as the analysis of new physics models which modify the strength of this coupling. I give an overview of the method and describe how we overcome the computational bottlenecks by using finite field reconstruction and the method of differential equations. The results are presented in terms of special functions suitable for numerical evaluation across the full physical phase space, making them useful for phenomenological applications.
This talk is based on arXiv:2107.14733
One of the main backgrounds in the multi-lepton decay channels of ttH production is ttW production. There is a slight tension between the theoretical predictions for this processes and what is needed to describe the data. In this talk the main cause for this tension will be outlined, and a solution, based on an improved version of the FxFx merging technique, will be proposed. This talk is based on arXiv:2108.07826.
It is an important task in the SM to constrain the CP property of the Higgs boson, which still exhibits a large uncertainty. We propose a novel observable at the LHC to probe the CP structure of Higgs coupling to the top quark by employing the linear polarization of gluon jets. The linear polarization induces a preferred direction for the azimuthal energy distribution in the gluon jet, which corresponds directly to the CP phase of the Higgs-top coupling. By constructing an infrared safe transverse spherocity observable for the gluon jet, we show that this new approach has a significant power in constraining the CP property of Higgs boson, complementary to the methods that are currently used in the experimental analysis.
A muon collider provides an interesting opportunity to test various aspects of Higgs physics and potential BSM models. For a muon collider, Vector-boson fusion provides the dominant channel for the production of Higgs bosons. We calculate the lowest and higher order Higgs jet distribution as a function of jet invariant mass for the super-renormalizable splitting $h\rightarrow hh$ and compare it to the background QCD jet distribution calculated from the NLL resummed cross section for $e^+$ $e^-$ annihilation. The qualitative difference between the two distributions shows up distinctly at collider center of mass energies greater than $10$ TeV as the peak of the QCD jets is pushed off to higher invariant jet masses, making it easier to observe the super-renormalizable and ultra-collinear $h\rightarrow hh$ jet distribution. This can also prove to be an important channel to test potential BSM models.
The muon collider is the ideal machine for reaching multi-TeV centre-of-mass energy and high luminosity lepton collisions, thanks to the low beamstrahlung and synchrotron radiation loss compared to $e^+$ $e^-$ colliders.
In such conditions, the number of produced Higgs bosons will allow to measure its couplings to fermions and bosons with an unprecedented precision.
However, in order to evaluate its physics reaches, the detector performance must be determined, since they may be strongly affected by very high fluxes of particles coming from muons decaying in circulating beams. In this contribution latest results on jet reconstruction and jet flavour identification performance, evaluated via full simulation of the muon collider detector, are presented.
Most recent results on the precision on the measurement of the Higgs production cross sections are shown. The signal and the physics background samples are fully simulated and reconstructed at 3 TeV center of mass energy, evaluating the effects of the beam-induced background on the detector performance.
The determination of the Higgs self-coupling from di-Higgs events with very high precision is one of the clearest benchmarks for the FCC-hh. Its potential has been well established already in several final states. In this talk studies into final states of the di-Higgs system which involve neutrinos are presented. The benefit of studying yet another di-Higgs final state is two-fold: First, any additional events included will add further precision to the measurement. Second, specifically neutrino channels will help to shed light on an experimental aspect for the FCC-hh which has not been well investigated yet: a robust reconstruction of the missing transverse momentum (ETMiss) is crucial for such analyses. It is is clear that ETMiss reconstruction at the FCC-hh will be extremely challenging due to the high pile-up environment, with average interactions per bunch crossing of the order of 1000. In particular, bbWW, bbττ and bbZZ signals are analysed in the final state with 2 light charged leptons in addition to ETMiss, using cut-based as well as multi-variate techniques. Their expected sensitivity is extracted, and the impact of different scenarios for systematic uncertainties, such as the worsening of the ETMiss resolution, is assessed.
The large dataset of about 3 ab-1 that will be collected at the High Luminosity LHC (HL-LHC) will be used to measure Higgs boson processes in detail. Studies based on current analyses have been carried out to understand the expected precision and limitations of these measurements. The large dataset will also allow for better sensitivity to di-Higgs processes and the Higgs boson self coupling. This talk will present the prospects for Higgs and di-Higgs results with the ATLAS detector at the HL-LHC.
We present results for Higgs boson pair production in gluon fusion
at NLO (2-loop) QCD including operators in the Standard Model Effective Field Theory (SMEFT) framework.
Contributions from subsets of higher order terms in $\frac{1}{\Lambda^2}$,
such as squared dimension-6 operators at cross section level and double operator insertions at amplitude level, are used as a proxy
for the study of truncation effects of the SMEFT expansion. The different truncation options are contrasted
to the non-linear Higgs Effective Field Theory (HEFT) framework for selected phenomenological examples.
The latest results on non-resonant Higgs boson pairs (HH) production in the bbtautau final state (where one Higgs boson decays into a pair of bottom quarks and the other decays into a pair of tau leptons) as well as in the multilepton final state will be presented. Both the gluon fusion and vector boson fusion production mechanisms are investigated. The bbtautau final state gives a good trade-off between a sizeable branching fraction (7.3%) and the purity of the tautau selection. This purity makes the bbtautau channel one of the most sensitive among those studied. These results considerably improve the latest ones published in 2016, profiting both from increased luminosity and novel analysis techniques that enhance the sensitivity of the search, i.e. extensive use of machine learning techniques for both event selection and signal extraction. The multilepton analysis selects 2-4 leptons and targets final states with 4 W bosons, 2 W bosons and 2 tau leptons, or 4 tau leptons.
Several physics scenarios beyond the Standard Model predict the existence of new particles that can subsequently decay into a pair of Higgs bosons. This talk summarises ATLAS searches for resonant HH production with LHC Run 2 data. Several final states are considered, arising from various combinations of Higgs boson decays.
This talk will present the latest CMS results on the search of non-resonant and resonant di-Higgs production, with one of the Higgs boson decaying to a pair of photons. The search for resonant di-Higgs production covers both the final state with two 125 GeV Higgs bosons as well as the final state with a 125 GeV Higgs boson and a different new scalar. The diphoton decay channel has excellent mass resolution and relatively low background and is hence the most sensitive or amongst the most sensitive final states for these searches.
At the LHC, a large range of different Higgs boson production modes and decay channels are studied. To obtain a full overview of the couplings between the Higgs boson and other particles, the data from these individual measurements of production and decay channels are combined. This is also the case for searches for HH production, where even more different final state combinations are possible, and where the best sensitivity is also reached by combining data from all these different channels. This talk focusses on the most recent combined measurements of single Higgs boson production and decay modes, as well as combined measurements of double Higgs boson production, with the CMS experiment. Constraints on the couplings between the Higgs boson and other SM particles, and on the Higgs boson self-interaction, will be presented.
In the Standard Model, the ground state of the Higgs field is not found at zero but instead corresponds to one of the degenerate solutions minimising the Higgs potential. In turn, this spontaneous electroweak symmetry breaking provides a mechanism for the mass generation of nearly all fundamental particles. The Standard Model makes a definite prediction for the Higgs boson self-coupling and thereby the shape of the Higgs potential. Experimentally, both can be probed through the production of Higgs boson pairs (HH), a rare process that presently receives a lot of attention at the LHC. In this talk, the latest HH searches by the ATLAS experiment are reported, with emphasis on the results obtained with the full LHC Run 2 dataset at 13 TeV. Non-resonant HH search results are interpreted both in terms of sensitivity to the Standard Model and as limits on the Higgs boson self-coupling. The Higgs boson self-coupling can be also constrained by exploiting higher-order electroweak corrections to single Higgs boson production. A combined measurement of both results yields the overall highest precision, and reduces model dependence by allowing for the simultaneous determination of the single Higgs boson couplings. Results for this combined measurement are also presented.
We consider the recent measurement of off-shell Higgs production by the CMS collaboration interpreted in terms of a width measurement of the Higgs boson and confront it with new physics in which the light quark Yukawa couplings are strongly enhanced. Even at the HL-LHC light quark Yukawa couplings of the first generation can only be constrained by factors of order a few hundred with respect to their Standard Model value. In what regards off-shell Higgs production, while enhanced light quark Yukawa couplings modify the Higgs width, a straightforward interpretation of the CMS measurement in terms of the width cannot be done as new production channels open up. Instead the dependence of the off-shell measurement on kinematic variables such as the invariant mass of the Z boson pair can be exploited to constrain new physics scenarios with enhanced light quark Yukawa couplings.
Precision studies of the properties of the Higgs bosons may provide a unique window for the discovery of new physics at the LHC. New phenomena can in particular be revealed in the search for lepton-flavor-violating or exotic decays of the Higgs bosons, as well as in their possible couplings to hidden-sector states that do not interact under Standard Model gauge transformations. This talk presents recent searches by the ATLAS experiment for decays of the Higgs bosons to new particles, using collision data at sqrt(s) = 13 TeV collected during the LHC Run 2.
Although the Higgs boson decay to four neutrinos predicted by the SM is inaccessibly small at the LHC, the Higgs boson branching fraction to invisible detector signatures can be significantly enhanced under various BSM scenarios. Searches for Higgs to invisible probe in particular Higgs portal models where the Higgs boson couples directly to dark matter, and the resulting constraints from the LHC explore a complementary dark matter candidate mass region lower than is accessible by the direct detection experiments. A summary of the latest searches for Higgs boson decays to invisible signatures is presented, using the full Run-2 dataset collected by the CMS experiment.
In the Standard Model, the branching ratio for Higgs boson decays to invisible final states is very small, but it can be significantly enhanced in extensions of the Standard Model. This talk presents searches for Higgs boson decays to invisible final states by the ATLAS experiment using the full Run 2 dataset of pp collisions collected at 13 TeV at the LHC, as well as their combination and interpretation.
This talk presents the results of a direct search for lepton-flavour-violating decays of the Higgs boson to e tau and mu tau final states with the ATLAS detector at the LHC. Both leptonically and hadronically decaying tau leptons are included and two different background estimation techniques are employed: A direct estimation of the background using MC, and a data-driven approach exploiting the electron-muon symmetry of the Standard Model. Both methods use data-derived estimations of misidentified background contributions, and MVA techniques to separate signal events from background.
The Higgs sector is a possible avenue for searches of BSM sources of CP violation, with V(V=W,Z)H production offering a way to separately probe the HWW and HZZ interactions, not possible in channels such as weak boson fusion. In this work, we search for CP-violating (CP-odd) EFT components in the HWW interaction via leptonic WH production - W(-> l \nu)H. This is a channel which allows high trigger efficiencies, good final state object resolution and good signal-to-background discrimination 0. Phenomenological studies in this channel 1 have proposed angular variables sensitive to these components, that require the full reconstruction of the W boson 4-vector and rely on the reconstruction of the longitudinal momentum of the neutrino. The latter is not only experimentally difficult (resulting in loss of resolution and efficiency) but, in addition, it is only possible up to a 2-fold ambiguity. The main goal of this work is to explore the simulation-based inference method SALLY (Score Approximates Likelihood LocallY) 3 to reconstruct a statistically optimal observable using the full kinematic information available in the event, bypassing the need for full neutrino reconstruction 4. The Fisher Information formalism is used to benchmark the sensitivity of different kinematic observables, angular observables and the SALLY method to this component, both inclusively as well as differentially, allowing us to define an optimal binning for the different observables 5. The expected 95% CL exclusion limits with both the Fisher Information formalism - mainly sensitive to the linear, CP-violating SM-EFT interference term - and the asymptotic likelihood ratio formalism are obtained and compared, allowing us a handle on the effect of the quadratic EFT term (CP-even by nature) on the sensitivity of the different observables.
The CP properties of the Higgs boson couplings to weak bosons can be probed in production by exploiting the Vector Boson Fusion process, or by studying the properties of the Higgs decay to two Z bosons. This talk presents the measurement of the CP properties to weak bosons by the ATLAS experiment using Higgs to two photon decays in VBF production, or Higgs to four leptons decays, and the full Run 2 dataset of pp collisions collected at 13 TeV at the LHC. The results are provided in the framework of Effective Field Theories.
Measurements of the inclusive and differential fiducial cross sections of Higgs boson decaying to a pair of photons are presented. The analysis is performed using proton-proton collisions data recorded with the CMS detector at the LHC at a centre-of-mass energy of 13 TeV and corresponding to an integrated luminosity of 138 fb−1. The measurements performed in fiducial regions target different production modes and are performed as function of several observables describing the diphoton system, the number of additional jets present in the events, and event-level observables. Two double differential measurements are also performed.
Higgs boson decays to two photons can be selected with high efficiency, and the very good invariant mass resolution allows a robust subtraction of the continuous backgrounds, making this channel an excellent tool both for precision measurements and searches for new phenomena involving the Higgs boson. This talk presents measurements of Simplified Template Cross Sections, differential and fiducial cross sections, as measured in the diphoton decay channel by the ATLAS experiment using the full Run 2 dataset of pp collision data collected at 13 TeV at the LHC, as well as generic searches for BSM phenomena where the Higgs boson is produced in association with other objects and decays in photon pairs. Measurements are further interpreted in the context of an Effective Field Theory.
The Higgs boson decays to two W bosons has the largest bosonic branching fraction and can be used to perform some of the most precise measurements of the Higgs boson production cross sections. This talk will present Higgs boson cross section measurements by the ATLAS experiment in the H->WW* decay channel using pp collision data collected at 13 TeV, including those for different Higgs boson production processes in the Simplified Template Cross Section framework, and fiducial and differential cross-sections.
With the large data set collected during Run 2 of the LHC, it is possible to go beyond inclusive Higgs boson cross section measurements. One way in which this is done is through the simplified template cross sections (STXS), which make use of several variables to divide up the phase space of the different Higgs boson production modes. The binning is designed to be particularly sensitive to possible BSM effects. This talk will discuss the latest STXS measurements from the CMS experiment, for example in the H->tautau and H->WW decay channels. The analysis techniques used to optimise the sensitivity to the different STXS bins will also be described.
Several Beyond Standard Model theories motivate an extended Higgs sector. Searches for additional Higgs bosons, based on these predictions, constitute an intensive subject of study within CMS. The two Higgs doublet models (2HDM) are by now heavily constrained. But models, where the two Higgs doublets are extended by one additional Higgs singlet complex field (2HDM+S), remain consistent with SM measurements as well as constraints from searches for additional Higgs bosons and supersymmetry with a considerable phase-space still unconstrained. The Higgs sector of the 2HDM+S models features seven physical states: three CP-even, two CP-odd, and two charged bosons. The current constraints from H(125) couplings measurements allow a non-negligible branching fraction for H(125) decays into non-SM particles, thus making the lightest pseudoscalar boson of the 2HDM+1S models, a1, potentially accessible in the H(125)→ a1a1 decay, with a sufficiently high rate to be detected at the LHC. This talk will present an overview of the searches performed in CMS on exotic decays of the Higgs boson to a pair of pseudoscalars during the Run 2 data-taking period. It will cover the wide spectrum of probed decay channels which span an extensive range of masses of the pseudoscalar boson from very boosted to non-boosted topologies.
Extensions of the Standard Model Higgs sector with a second Higgs doublet allow for the existence of charged Higgs bosons as well as heavy pseudoscalar Higgs bosons. The heavy pseudoscalars can decay into a Z boson and a lighter scalar Higgs boson, which could be either the established 125 GeV state, or a new heavier sibling. Charged Higgs bosons are probed in various final states, including decays to a W boson and another lighter scalar. This presentation discusses recent results from the CMS experiment based on the Run 2 dataset.
The discovery of the Higgs boson with the mass of about 125 GeV completed the particle content predicted by the Standard Model. Even though this model is well established and consistent with many measurements, it is not capable to solely explain some observations. Many extensions of the Standard Model addressing such shortcomings introduce additional neutral Higgs-like bosons. The current status of searches for such new neutral Higgs bosons based on the full LHC Run 2 dataset of the ATLAS experiment at 13 TeV are presented.
Although many suggestions for BSM searches at future colliders exist, most of them concentrate on additional scalars that have masses higher than the current SM scalar mass. I will give a short overview on the current status of models and searches for scalars with masses below this. Based on https://arxiv.org/abs/2205.09687
We discuss theoretical and experimental constraints on extended Higgs models with large quantum corrections. Such large quantum effects play an important role to realize the strongly first-order electroweak phase transition. We use a new Higgs EFT describing the strongly first-order phase transition in order to discuss model independent results. We show that the parameter region satisfying the sphaleron decoupling condition can be searched by future collider experiments, gravitational wave observations and primordial black hole observations. This talk is based on the following reference and work:
[1] S. Kanemura, R. Nagai and M. Tanaka, JHEP 06 (2022) 027 [arXiv: 2202.12774].
[2] K. Hashino, S. Kanemura, T. Takahashi and M. Tanaka, Work in progress.
Recent analyses on high-energy inclusive Higgs-boson rates in proton collisions via the gluon fusion channel, matched with the state of-the-art fixed-order N$^3$LO accuracy, have shown that the impact of high-energy resummation corrections reaches 10% at the FCC nominal energies. This supports the statement that electroweak physics at 100 TeV is expected to receive relevant contributions from small-$x$ physics. In this talk we will present novel predictions for transverse-momentum and rapidity distributions sensitive the inclusive emission of a Higgs boson in association with a light-flavored jet in proton collisions, calculated within the NLL accuracy of the energy-logarithmic resummation. We will highlight how high-energy signals for this process are already present and visible at current LHC energies, and they become very important at FCC ones. We come out with the message that the improvement of fixed-order calculations on Higgs-sensitive QCD distributions is a core ingredient to reach the precision level of the description of observables relevant for the Higgs physics at the FCC.
The Standard Model predicts several rare Higgs boson decay channels, among which are decays to a Z boson and a photon, H to Zgamma, and to a low-mass lepton pair and a photon H to llgamma, and a pair of muon. The observation of Zgamma decays could open the possibility of studying the CP and coupling properties of the Higgs boson in a complementary way to other analyses. In addition, the search for Higgs decays into a vector quarkonium state and a photon provides access to charm- and bottom-quark couplings alternative to the direct H->bb/cc search. Several results for decays based on pp collision data collected at 13 TeV will be presented.
At high energies, fixed-order predictions for the production of a Higgs boson together with one or more jets suffer from large logarithms in invariant masses over transverse momenta. We resum these high-energy logarithms to all orders using the High Energy Jets (HEJ) framework, retaining the exact dependence on the top-quark mass. We compare our predictions to ATLAS and CMS measurements at 8 and 13 TeV.
Collider experiments will achieve percent level precision measurements of several processes key to answer some of the most pressing questions of contemporary particle physics. In this talk I will show that the capability to predict and describe such observables at next-to-next-to-next-to-leading order (N3LO) in QCD perturbation theory is crucial to fully exploit these experimental measurements.
I will describe how to compute differential distributions via slicing methods and illustrate the calculation of the N3LO TMD beam functions which were the missing ingredient for extending these techniques to N3LO.
Finally, I will present the recent calculation of the rapidity anomalous dimension (Collins-Soper kernel) to N4LO needed for the resummation of the Higgs transverse momentum spectrum at fourth logarithmic accuracy (N4LL).
We present NLO QCD corrections to ZH production in gluon fusion, including the effects of the top-quark mass. Our results are obtained by combining virtual corrections evaluated numerically using sector decomposition with virtual corrections obtained in an high-energy expansion.
We discuss the uncertainties related to the top-quark mass renormalization scheme and we present phenomenological results.
We present the calculation of the virtual QCD corrections to gg → HH and gg → ZH. The results are obtained combining an expansion in the small transverse momentum of the final particles with an expansion valid at high energies, and extending the range of validity of both expansions using Padé approximants. This approach can reproduce the available numerical results retaining the exact top quark mass dependence with an accuracy below the 1% level. In the case of ZH production, we use our results to obtain an analytical evaluation of the gg->ZH channel at NLO in QCD, including the effects of the change of the top quark mass renormalization scheme.
Higgs-boson pair production at hadron colliders is dominantly mediated by
the loop-induced gluon-fusion process gg→HH that is generated by heavy
top loops within the Standard Model with a minor per-cent level
contamination of bottom-loop contributions. The QCD corrections turn out
to be large for this process. In this talk, we discuss the
top-Yukawa-induced part of the electroweak corrections to this process and
their relation to an effective trilinear Higgs coupling with integrated
out top-quark contributions.
In this talk, I will present a first look at the two-loop electroweak
corrections to Higgs boson pair production in gluon-fusion, which
might have a sizeable impact on the cross section. We have performed an
analytic calculation of the two-loop diagrams contributing
to gg->HH where a virtual Higgs boson is exchanged in the top quark loop.
I will briefly describe our method used to solve massive two-loop box
integrals and then discuss results for the form factors. We show that
precise results can be obtained, even for $p_t \approx 100$ GeV and above.
Extensions of the Higgs sector beyond the standard model, in particular models with two Higgs doublets and possibly additional singlets, predict the existence of additional particles in the Higgs sector. These additional particles include a neutral Higgs boson with a large allowed mass region. When the mass of the neutral Higgs boson is less than half the Higgs boson mass, an important search channel is via decays of the SM-like Higgs boson that include these additional neutral bosons. These decays leave a rich variety of possible experimental signatures, with the dominant decay mode depending on the neutral Higgs boson mass range. This talk summarizes the latest search results for light neutral Higgs bosons via SM-like Higgs boson decays, using the full LHC Run-2 dataset collected by the CMS experiment.
The MicroBooNE detector is a 60 m$^3$ active volume liquid argon time projection chamber located at Fermilab approximately 100 m from a high intensity stopped kaon source. We use this setup to search for a light, long-lived scalar boson that mixes with the Higgs boson and could be produced in rare kaon decays. We present results of our search for different dilepton signatures of these scalar boson decays, and set world-leading direct limits on the Higgs–scalar mixing angle for scalar boson masses below 275 MeV.
Based on arXiv:2110.10691
We study exotic Higgs decays $h \to Z X$, with $X$ an invisible beyond the Standard Model (SM) particle, resulting in a semi-dark final state. Such exotic Higgs decays may occur in theories of axion-like-particles (ALPs), dark photons or pseudoscalar mediators between the SM and dark matter. The SM process $h\to Z\nu\bar{\nu}$ represents an irreducible ``neutrino floor'' background to these new physics searches, providing also a target experimental sensitivity for them. We analyze $h \to Z + \text{invisible}$ searches at the LHC and a future ILC, showing that these exotic Higgs decays can yield sensitivity to unexplored regions of parameter space for ALPs and dark matter models.
The search for dark photon (y_d) in resonant mono-photon signatures from the Higgs boson decay H->yy_d in the ZH production mode with Z->ll has been performed using 139 fb-1 of proton???proton collision data recorded with the ATLAS detector at a centre-of-mass energy sqrt(s) = 13 TeV at the Large Hadron Collider during the 2015-2018 Run 2. A global fit to the Boosted Decision Tree (BDT) score, including all background processes, has been performed to estimate the excess of events that could be interpreted as a possible signature of H->yy_d in the final state. Dominant backgrounds, consisting in fake Etmiss and e->y, have been estimated using data-driven techniques: an ABCD method has been implemented for fake Etmiss while e->y fake-rates have been estimated via Z->ee boson decay and applied in dedicated probe-e CRs. Results covering a y_d mass range from massless up to 40 GeV are provided in terms of limits on the branching ratio of such a decay mode of the Higgs boson.