Present day high statistic tau lepton experimental samples, require continuous revision of simulation precision. This is especially important for multi-dimensional signatures. That is in partiucular important in context of anomalous couplings.
Also, because evolution of software environments, completion of programs migration to C++ as well as study of new effects become of ever greater...
In the Tau section of the HFLAV 2023 report (arXiv:2411.18639 [hep-ex]) we present an improved global fit of the tau branching fractions and new combinations of tau lepton-flavour-violating (LFV) upper limits. The branching fraction fit includes recent measurements and furthermore since this report features nuisance fit parameters. The HFLAV fit is now...
Semileptonic τ decays mainly proceed via interactions between charged lepton and quark currents. The hadronization of the quark current is intrinsically nonperturbative and generally cannot be addressed analytically. In this work, we propose using symmetry arguments alone to construct clean angular observables, which, within the Standard Model and in the absence of long-distance...
Tau leptons play a central role in the search for physics beyond the Standard Model at the LHC. This talk presents recent results from the CMS Collaboration on both direct searches for new physics with taus and precision tests of lepton flavor universality. Novel reconstruction techniques, targeting taus with low transverse momentum and those produced at displaced vertices, open sensitivity to...
Many theories beyond the Standard Model predict new phenomena, such as leptoquarks, vector like leptons, supersymmetry, new scalars or heavy leptons, in final states with isolated taus reconstructed using standard techniques. Searches for new physics with such signatures, produced either resonantly or non-resonantly, are performed using the ATLAS experiment at the LHC. The most recent results...
Tau leptons play a crucial role in studies of the Higgs boson and searches for Beyond the Standard Model physics at the present LHC and in its high luminosity upgrade. This talk presents the latest advancements in the reconstruction and identification of hadronic decays of tau leptons at the CMS experiment, both at the online and offline levels. The tau identification algorithm deployed for...
Many extensions of the Standard Model predict new phenomena like beyond-the-Standard-Model couplings to the Higgs boson, charged Higgs, Heavy neutral lepton, supersymmetry, among others. In this talk, the latest searches latest from the ATLAS experiment will be reported, with emphasis on the final states using special tau reconstruction techniques like merged or boosted tau topologies as well...
The H->tau tau decay mode has a relatively high BR and good S/B ratio when considering advanced techniques to reconstruct and identify tau leptons in all possible decay modes. This enables the search of rare process, as non-resonant di-Higgs production, where one of the Higgs boson decays to ditaus. Possible channels involve H->gamma gamma, H->bb, associated with the H->tau tau decay. This...
The rates of lepton-flavour, lepton-number, and baryon-number violating $\tau$ decays are enhanced in many beyond-the-standard-model theories. The Belle and Belle II experiments have collected samples of $e^{+}e^{-}$ collision data containing a huge number of $e^{+}e^{-} \rightarrow \tau^{+}\tau^{-}$ events with constrained kinematics and low backgrounds, providing an ideal environment to...
I present a concise overview of tau flavor violation and the broad opportunities it offers, with a focus on non-standard decay channels and their underlying theoretical motivations.
A measurement of the key cross section e+e- to pi+pi- for hadronic vacuum polarization (HVP)is presented with the full BABAR statistics using a new method not relying on particle ID to separate pions ans muons, therefore independent from the 2009 analysis. This result should play an important role to clarify the presently rather confused situation where large discrepancies are observed between...
Despite being a highly sensitive probe for physics beyond the Standard Model (BSM), the anomalous magnetic moment of the tau lepton $a_\tau$ remains significantly less explored than those of other leptons. This talk presents a promising path to measure $a_\tau$ with a precision of $10^-5$, a level crucial for imposing meaningful constraints on BSM theories. Achieving this precision...
https://journals.aps.org/prd/abstract/10.1103/PhysRevD.110.092016
We will present the latest limits on the anomalous magnetic moment (g – 2) of the tau lepton at CMS. These are obtained from photon-induced processes in heavy-ion collisions, or in proton-proton collisions.
In ultra-relativistic heavy-ion collisions, high rates of $\gamma\gamma$ processes occur through the interaction of the large electromagnetic fields of the heavy nuclei. For large impact parameters between the nuclei, i.e. interaction distances larger than the nuclei's radii, the di-photon interaction can be the only one taking place, leading to very clean signatures in the detector. One of...
We discuss recent results leading to a new understanding of one of the two
main approaches to determining $\alpha_s$ from finite-energy sum rule analyses of non-strange hadronic $\tau$ decay data. This approach involves fits to sets of differently weighted spectral integrals with a single common upper endpoint, $s=s_0$, in which several in-principle-present, higher-dimension condensate...
The inclusive hadronic width of the tau lepton can be rigorously analysed with quantum-field-theory techniques. Precise experimental measurements of the invariant-mass distribution of the final hadrons make possible to perform an accurate low-energy determination of the strong coupling and extract useful information about non-perturbative QCD parameters. An overview of the current status will...
Quantum state tomography involves a series of measurements that provide complete information about the quantum state describing the system under investigation. In this presentation, I review the capabilities of this technique for studying the spin state of tau lepton pairs produced at current and future lepton colliders. The reconstruction of the quantum state describing these systems allows...
The existence and unknown nature of dark matter motivates dark sector searches at accelerators. The Belle experiment has collected samples of $e^{+}e^{-}$ collision data containing a huge number of $e^{+}e^{-} \rightarrow \tau^{+}\tau^{-}$ events with constrained kinematics and low backgrounds, enabling several world-leading dark matter searches in the sub-GeV mass region. Using 800...
I will review the current phenomenological status of B decays involving tau leptons in the final state and what is the interplay with broader class of processes involving tau.
I will emphasize how tau decays grant us access into detailed structure of interactions in B physics.
In the SM, the electroweak bosons couple to the three lepton families with the same strength having the only difference in their behaviour due to the difference in mass. The current measurements of the ratios of branching fractions for b-hadrons decaying into final states with different lepton flavours deviate of the order of 3 σ with respect to the Standar Model. This talk presents recent...
In this talk, we will review the latest Belle II results on b -> s tau tau decays and tests of lepton flavour universality in b -> c tau nu decays.
Several discrepant measurements have been observed by LHCb and other experiments in b→cτν decays over the past few years. If these are due to new physics beyond the Standard Model, several models suggest an associated large enhancement in the branching fractions of b→sττ decays. Such decays have not been observed yet, and the existing upper limits which have been set are several orders of...
The MUonE experiment at CERN aims to provide an independent measurement of the leading-order hadronic contribution to the muon g-2 ($a_{\mu}^\text{HVP}$), complementary to the existing ones. The innovative approach proposed by MUonE is based on the measurement of the hadronic contribution to the running of the QED coupling, which can be extracted from a precise measurement of the shape of the...
Tau data, especially the 2-pion spectral function, can be used to compute the HVP contribution to the SM muon g-2 prediction after correcting for isospin violations between tau and e+e-. These corrections are usually computed theoretically with uncertainties sometimes difficult to establish. We present here a data-based evaluation of the most critical correction to the charged-current pion...
The hadronic $\tau$ decay, $\tau\rightarrow\pi\pi^0\nu_\tau$, provides an independent way to compute the HVP contribution to the muon $g-2$ Standard Model (SM) prediction, provided one is able to reliably evaluate the relevant isospin breaking (IB) corrections. I will present a dispersive approach to the evaluation of the IB corrections relating $\tau\rightarrow\pi\pi^0\nu_\tau$ to...
The Mu2e experiment will search for coherent neutrinoless conversion of a negative muon into an electron in the field of an aluminium nucleus. Observation of this process would be a signature of Charged Lepton Flavor Violation (CLFV), a Beyond the Standard Model (BSM) process predicted by various theories. Mu2e aims to improve the current limit by four orders of magnitude, reaching a single...
Charged lepton flavor violation is a popular target in searches for new physics. We demonstrate how the search for violations of an accidental symmetry of the Standard Model can also be connected to the search for violations of more fundamental symmetries. Working in the Standard Model Extension, a Lorentz- and CPT-violating effective field theory, we investigate the conversion of a muon to...
Separating tracks from cascades in IceCube is critical for precision oscillation measurements and tau-appearance searches, yet sparse hit patterns at lower energies limit the reach of standard topology-based methods. We address this challenge with WavePID, a new variable engineered based on the timing profile of single-DOM waveforms at 5-100 GeV, inspired by earlier PID results in...
Water Cherenkov detectors have demonstrated exceptional sensitivity in
neutrino observation over the years. The Hyper-Kamiokande (Hyper-K),
the third generation of underground detectors in Japan, represents a
significant advancement in both sensitivity and scalability. Hyper-K will
act as the far detector for a long-baseline neutrino oscillation experiment
using the upgraded 1.3 MW J-PARC...
The tau neutrino is one of the least well studied particles in the Standard Model, with an overall measured statistics of about 2000 events. KM3NeT/ORCA is a water Cherenkov detector currently under construction in the Mediterranean Sea that aims to determine the neutrino mass ordering. It is optimised for the detection of atmospheric neutrinos in the 1-100 GeV range. While the atmospheric...
In this talk we present the outcome of a stand-alone feasibility study using RapidSim simulation software that demonstrates that the Large Hadron Collider beauty (LHCb) experiment will be capable of observing the decays $B^+\rightarrow\tau^+\nu_{\tau}$ and $B_c^+\rightarrow\tau^+\nu_{\tau}$ using the data that is being collecting during Run 3 of the LHC. Our proposed analysis exploits the...
Charged Lepton Flavour Violation (cLFV) is strongly suppressed in the Standard Model and therefore represents a sensitive probe for physics beyond it. Recently, the LHCb experiment has performed dedicated searches for cLFV, both in semileptonic b-hadron decays and in purely leptonic tau decays, placing competitive bounds on several decay modes. These results provide relevant constraints on a...
The $K^{+}\rightarrow\pi^{+}\nu\bar{\nu}$ decay is a golden mode for flavour physics. Its branching ratio is predicted with high precision by the Standard Model to be less than $10^{-10}$, and this decay mode is highly sensitive to indirect effects of new physics up to the highest mass scales. A new measurement of the $K^{+}\rightarrow\pi^{+}\nu\bar{\nu}$ decay by the NA62 experiment at the...
The SND@LHC experiment was designed to perform measurements with neutrinos produced at the LHC within the unexplored pseudo-rapidity range of 7.2 < 𝜂 < 8.6. Located 480 m downstream of IP1 in the unused TI18 tunnel, this compact and stand-alone experiment employs a hybrid detector system consisting of 800 kg of tungsten plates interleaved with emulsion and electronic trackers, complemented by...
The super tau-charm facility proposed in China, is suppose to produce 3.5 billion tau pairs per year in the energy region of 4 to 5 GeV. Besides, the STCF covers the threshold of tau pairs. Based on thses samples, general topics are proposed at STCF, e.g., cLFV processes, $|V_{us}|$ measurements, alpha_s and tau mass measurements. Novel topics are proposed at well, e.g., tau atoms. In this...
We estimate the precision at FCC-ee on the measurements of the tau mass, lifetime, leptonic branching fractions, and on the searches for lepton-flavour-violating branching fractions $\tau \to \mu\gamma$ and $\tau \to 3\mu$. We compute the estimated precision on the lepton flavour universality tests, considering the 2nd-order QED radiative corrections and estimating the radiative corrections...
Upgrading the SuperKEKB e+e− collider with polarized electron beams, the Chiral Belle project, provides new and unique opportunities for searches for new physics via precision electroweak and other measurements, including measurements involving the tau lepton.
These include measurements the neutral current vector couplings via left-right asymmetry (ALR) measurements in annihilations to pairs...
