Argentine PH-Institute

23 Oct 2017, 09:00 → 27 Oct 2017, 17:00 America/Argentina/Buenos_Aires

ICAS

Alejandro Szynkman, Daniel De Florian (Laboratorio de Fisica Teorica Departamento de Fisica), Ezequiel Alvarez, Leandro Da Rold

This PH-Institute is devoted to discuss the phenomenology of searches of Physics Beyond the Standard Model, mainly at the LHC.

There will be 10-15 people during a week, and have 2 talks at 11AM and 4PM.  In the mean time each one has a desk with internet to work and discuss with other colleagues.

Registration is only by invitation.
 

Monday 23 October

1 Registration

10:30 Coffee served

2 Searches for top and Higgs compositeness at the LHC

A possible extension of the Standard Model that addresses the hierarchy problem
in a natural way involves the existence of a new strongly-interacting sector, of which
the Higgs boson would be a pseudo-Goldstone boson of a spontaneously-broken global
symmetry. One particular realization of this scenario, referred to as "Composite Higgs",
predicts the existence of new fermionic resonances (referred to as vector-like quarks),
which can be produced in pairs or single and have multiple decay modes, giving striking
experimental signatures at the LHC. Another prediction is the existence of heavy bosonic
resonances from the composite sector that would predominantly couple to third-generation
quarks, leading to increased 4-top and ttbb production at high energies. In this talk we
will review the strategies and challenges, as well as the latest results, of this research
program at the LHC. We will also discuss the prospects for Run 2 and future LHC runs.

Speaker: Prof. Aurelio Juste (IFAE)

14:00 Coffee served

3 Search strategies for pair production of heavy Higgs bosons decaying invisibly at the LHC

The search for heavy Higgs bosons at the LHC represents an intense experimental program, carried out by the ATLAS and CMS collaborations, as well as the hunt of invisible Higgs decays and dark matter candidates. No significant deviations from the SM backgrounds have been observed in any of these searches, imposing important constraints over the parameter space of different new physics models with an extended Higgs sector. Here we discuss an alternative search strategy for heavy Higgs bosons decaying invisibly at the LHC, focusing on the pair production of a heavy scalar $H$ together with a pseudoscalar $A$, through the production mode $q \bar q \to Z^\ast \to HA$. We identify as the most promising signal the final state made up by $4b + E_T^\text{miss}$, coming from the heavy scalar decay mode $H \to hh \to b \bar b b \bar b$, being $h$ the discovered SM-like Higgs boson of 125 GeV, together with the invisible channel of the pseudoscalar. We work within the context of simplified MSSM scenarios that contain quite heavy sfermions of most types with ${\cal O}(10)$ TeV masses, while the stops are heavy enough to reproduce the 125 GeV mass for the lightest SM-like Higgs boson. By contrast, the gauginos/higgsinos and the heavy MSSM Higgs bosons have masses near the EW scale. Our search strategies, for a LHC center-of-mass energy of $\sqrt{s} =$ 14 TeV, allow us to obtain statistical significances of the signal over the SM backgrounds with values up to $\sim$ 1.6$\sigma$ and $\sim$ 3$\sigma$, for total integrated luminosities of 300 fb$^{-1}$ and 1000 fb$^{-1}$, respectively.

Speaker: Ernesto Arganda (UNLP, La Plata)

Tuesday 24 October

09:00 Coffee served

4 pp -> hh @ LHC

Speakers: Daniel De Florian (ICAS), Ignacio Fabre (ICAs)

14:00 Coffee served

5 LFV Higgs decays in low-scale seesaw models within the mass insertion approximation

In this talk I present a new computation of the Lepton Flavor Violating
Higgs decays that are generated radiatively to one-loop from heavy
right-handed neutrinos. We work within the context of the Inverse Seesaw
model with three right-handed neutrinos and three extra singlets, but the
results could be generalized to other Low Scale Seesaw models. The novelty
of our computation is that it uses a completely different method by means
of the Mass Insertion Approximation which works with the electroweak
interaction states instead of the usual 9 physical neutrino mass
eigenstates of the Inverse Seesaw model. This method also allows us to
write the analytical results explicitly in terms of the most relevant
model parameters, that are the neutrino Yukawa coupling matrix and the
right-handed mass matrix, which is very convenient for a phenomenological
analysis.
We also study numerically the goodness of the Mass Insertion Approximation
results. In the last part we present the computation of the relevant
one-loop effective vertex for the Lepton Flavor Violating Higgs decay
which is derived from a large right-handed neutrino mass expansion of the
form factors. We believe that our simple formula found for this effective
vertex can be of interest for other researchers who wish to estimate the
corresponding rates in a fast way in terms of their own preferred input
values for the relevant model parameters.

Speaker: Roberto Morales (UNLP)

6 Measuring Vtd at the LHC

We propose a direct measurement of the CKM element Vtd at the LHC. Taking profit of the imbalance between d and d¯ quark content in the proton, we show that a non-zero Vtd induces a charge asymmetry in the tW associated production. The main backgrounds to this process, tt¯ production, and tW associated production mediated by Vtb, give charge symmetric contributions at leading order in QCD. Therefore, using specific kinematic features of the signal, we construct a charge asymmetry in the di-lepton final state which, due also to a reduction of systematic uncertainties in the asymmetry, is potentially sensitive to Vtd suppressed effects. In particular, using signal and background simulations up to detector level, we show that this new observable could improve the current direct upper bound on |Vtd| already with existing LHC data. We also project that |Vtd| values down to ∼10 times the Standard Model prediction could be probed in the high luminosity phase of the LHC.

Speaker: Mariel Estevez (ICAS)

Wednesday 25 October

09:00 Coffee served

7 Searching for SUSY at the LHC: promising signals for left sneutrino LSP and other possibilities

Supersymmetric extensions of the standard model provides a solution the the hierarchy problem and the possibility to give observable signals at the LHC. When R-parity is broken and the right-handed neutrinos are included in the spectrum many interesting interpretations are possible. After a brief introduction of the simplest model including many useful interpretations and desirable properties, we are going to discuss possible interesting signals in some particular cases. For instance for a left sneutrino LSP, there are two dominant channels, direct production via a Z boson, or production via a W± decaying into a left sneutrino and a left slepton next-to-LSP (NLSP), with the latter decaying into another left sneutrino plus a very soft W± subproduct. From the decay of a pair of left sneutrinos LSPs of any family, a diphoton signal plus missing transverse energy (MET) from neutrinos can be present. In addition, in the case of a pair of tau left sneutrinos LSPs, given the large value of the tau Yukawa coupling, diphoton plus leptons and/or multileptons can appear.

Speaker: Daniel Lopz Fogliani (UBA, Buenos Aires)

14:00 Coffee served

8 TBA

Speaker: Marcela Carena (FermiLab)

Thursday 26 October

09:00 Coffee served

9 UBA@ATLAS

Analysis and implementations by the UBA group at ATLAS

Speaker: Gustavo Otero y Garzon (UBA)

14:00 Coffee served

10 (some) dark matter at (some) colliders

Speaker: Prof. Jose Zurita (KIT)

Friday 27 October

09:30 Coffee served

11 TBA

Speaker: Leandro Da Rold (CAB, Bariloche)

14:00 Coffee served

12 Enlarging the Regions of the MSSM Parameter Space for large tan beta via SUSY Decays of the Heavy Higgs Bosons

In the Minimal Supersymmetric Standard Model (MSSM) searches for the heaviest CP-even and CP-odd Higgs H, A to tau-lepton pairs severely constrain the parameter region for large values of tanβ and light Higgs bosons H, A. We demonstrate how the exper- imental constraint can be avoided by new decays to light third-generation sfermions, whose left-right couplings to H can be maximised in regions of large trilinear couplings Ab, Aτ for sbottoms and staus, or large supersymmetric (SUSY) Higgs mass μ for stops. Due to the tanβ-enhancement in the production cross-sections via gluon-fusion and in association with bottom-quark pairs for H and A, we find that down-type sfermions, in particular, sbottoms perform a better job in allowing more parameter space than up-type sfermions such as stops, which require much larger values of μ to compensate for tanβ. Vacuum stability as well as flavour observables constraints and direct searches for SUSY particles are imposed. We also associate the lightest CP-even Higgs with the observed 125 GeV SM-like Higgs and impose the experimental constraints from the LHC.

Speaker: Anibal Medina (UNLP, La Plata)