scholarly journals Measurements of Higgs-boson decays to leptons with the ATLAS detector

2019 ◽  
Author(s):  
Lara Katharina Schildgen
Keyword(s):  
Higgs Boson ◽  
Standard Model ◽  
Precise Measurement ◽  
New Physics ◽  
Muon Decay ◽  
Tau Leptons ◽  
Beyond The Standard Model ◽  
Yukawa Couplings ◽  
Higgs Boson Decaying ◽  
The Standard Model

Since its discovery in 2012, the Higgs boson has served as an important probe for precision measurements of the Standard Model and for searches for new physics beyond the Standard Model. One major goal of the LHC is the precise measurement of the Higgs Yukawa couplings to fermions. The latest ATLAS results of measurements of the Higgs boson decaying to leptons are presented, namely the cross-section measurement of the Higgs boson decay to two tau leptons and the searches for the di-muon decay and lepton-flavour-violating decays of the Higgs boson.

scholarly journals The CKM unitarity problem: a trace of new physics at the TeV scale?

2020 ◽  
Vol 80 (2) ◽  
Author(s):  
Benedetta Belfatto ◽  
Revaz Beradze ◽  
Zurab Berezhiani
Keyword(s):  
Standard Model ◽  
Decay Constant ◽  
New Physics ◽  
Muon Decay ◽  
Beyond The Standard Model ◽  
Neutron Lifetime ◽  
Gauge Bosons ◽  
Family Symmetry ◽  
Ckm Matrix ◽  
The Standard Model

Abstract After the recent high precision determinations of $$V_{us}$$Vus and $$V_{ud}$$Vud, the first row of the CKM matrix shows more than $$4\sigma $$4σ deviation from unitarity. Two possible scenarios beyond the Standard Model can be investigated in order to fill the gap. If a 4th non-sequential quark $$b'$$b′ (a vector-like weak isosinglet) participates in the mixing, with $$\vert V_{ub'} \vert \sim 0.04$$|Vub′|∼0.04, then its mass should be no more than 6 TeV or so. A different solution can come from the introduction of the gauge horizontal family symmetry $$SU(3)_\ell $$SU(3)ℓ acting between the lepton families and spontaneously broken at the scale of about 6 TeV. Since the gauge bosons of this symmetry contribute to muon decay in interference with Standard Model, the Fermi constant is slightly smaller than the muon decay constant so that unitarity is recovered. Also the neutron lifetime problem, that is about $$4\sigma $$4σ discrepancy between the neutron lifetimes measured in beam and trap experiments, is discussed in the light of the these determinations of the CKM matrix elements.

The long journey to the Higgs boson and beyond at the LHC: Emphasis on CMS

2016 ◽  
Vol 31 (32) ◽  
pp. 1630058
Author(s):  
Tejinder Singh Virdee
Keyword(s):  
Higgs Boson ◽  
Standard Model ◽  
Hadron Collider ◽  
Heavy Particle ◽  
New Physics ◽  
Beyond The Standard Model ◽  
Cms Experiment ◽  
The Standard Model ◽  
Electroweak Sector ◽  
The One

Since 2010 there has been a rich harvest of results on standard model physics by the ATLAS and CMS experiments operating on the Large Hadron Collider. In the summer of 2012, a spectacular discovery was made by these experiments of a new, heavy particle. All the subsequently analysed data point strongly to the properties of this particle as those expected for the Higgs boson associated with the Brout–Englert–Higgs mechanism postulated to explain the spontaneous symmetry breaking in the electroweak sector, thereby explaining how elementary particles acquire mass. This article focuses on the CMS experiment, the technological challenges encountered in its construction, describing some of the physics results obtained so far, including the discovery of the Higgs boson, and searches for the widely anticipated new physics beyond the standard model, and peer into the future involving the high-luminosity phase of the LHC. This article is complementary to the one by Peter Jenni4 that focuses on the ATLAS experiment.

scholarly journals THE STUDY OF THE PROPERTIES OF THE EXTENDED HIGGS BOSON SECTOR WITHIN hMSSM MODEL

2019 ◽  
pp. 3-10
Author(s):  
T.V. Obikhod ◽  
E.A. Petrenko
Keyword(s):  
Higgs Boson ◽  
Standard Model ◽  
Cross Sections ◽  
Branching Fractions ◽  
New Physics ◽  
Boson Mass ◽  
Atlas Collaboration ◽  
Beyond The Standard Model ◽  
Higgs Boson Mass ◽  
The Standard Model

Using the latest experimental data, performed by ATLAS Collaboration and within the framework of the Minimal Supersymmetric Standard Model, we presented the calculations for cross sections times branching fractions, σ×Br, as a functions of the CP-even, H, Higgs boson mass, CP-odd, A, Higgs boson mass and charged, H±, Higgs boson mass. Using the restricted parameter set, received from the hMSSM+HDECAY and ”low-tb-high” scenarios, with the help of the computer programs SOFTSUSY, Prospino and SusHi, we received the large values of σ ×Br for A and H bosons at tanβ=2 for the planned 14 TeV at the LHC and found the large σ ×Br at tanβ=30 for charged Higgs boson. The obtained results are of experimental interest as they are connected with the experimental searches for new physics beyond the Standard Model at the LHC.

scholarly journals Disentangling QCD and new physics in D → πℓ+ℓ−

2021 ◽  
Vol 2021 (4) ◽  
Author(s):  
Aoife Bharucha ◽  
Diogo Boito ◽  
Cédric Méaux
Keyword(s):  
Standard Model ◽  
Branching Ratio ◽  
Branching Ratios ◽  
New Physics ◽  
Operator Product ◽  
Beyond The Standard Model ◽  
Spectral Functions ◽  
The Standard Model ◽  
Model Independent ◽  
Weak Annihilation

Abstract In this paper we consider the decay D+ → π+ℓ+ℓ−, addressing in particular the resonance contributions as well as the relatively large contributions from the weak annihilation diagrams. For the weak annihilation diagrams we include known results from QCD factorisation at low q2 and at high q2, adapting the existing calculation for B decays in the Operator Product Expansion. The hadronic resonance contributions are obtained through a dispersion relation, modelling the spectral functions as towers of Regge-like resonances in each channel, as suggested by Shifman, imposing the partonic behaviour in the deep Euclidean. The parameters of the model are extracted using e+e− → (hadrons) and τ → (hadrons) + ντ data as well as the branching ratios for the resonant decays D+ → π+R(R → ℓ+ℓ−), with R = ρ, ω, and ϕ. We perform a thorough error analysis, and present our results for the Standard Model differential branching ratio as a function of q2. Focusing then on the observables FH and AFB, we consider the sensitivity of this channel to effects of physics beyond the Standard Model, both in a model independent way and for the case of leptoquarks.

scholarly journals Indirect $$ \mathcal{CP} $$ probes of the Higgs-top-quark interaction: current LHC constraints and future opportunities

2020 ◽  
Vol 2020 (11) ◽  
Author(s):  
Henning Bahl ◽  
Philip Bechtle ◽  
Sven Heinemeyer ◽  
Judith Katzy ◽  
Tobias Klingl ◽  
...  
Keyword(s):  
Higgs Boson ◽  
Standard Model ◽  
Top Quark ◽  
Decay Channel ◽  
New Physics ◽  
Current Data ◽  
Quark Interaction ◽  
The Standard Model ◽  
Vector Bosons ◽  
Selection Of

Abstract The $$ \mathcal{CP} $$ CP structure of the Higgs boson in its coupling to the particles of the Standard Model is amongst the most important Higgs boson properties which have not yet been constrained with high precision. In this study, all relevant inclusive and differential Higgs boson measurements from the ATLAS and CMS experiments are used to constrain the $$ \mathcal{CP} $$ CP -nature of the top-Yukawa interaction. The model dependence of the constraints is studied by successively allowing for new physics contributions to the couplings of the Higgs boson to massive vector bosons, to photons, and to gluons. In the most general case, we find that the current data still permits a significant $$ \mathcal{CP} $$ CP -odd component in the top-Yukawa coupling. Furthermore, we explore the prospects to further constrain the $$ \mathcal{CP} $$ CP properties of this coupling with future LHC data by determining tH production rates independently from possible accompanying variations of the $$ t\overline{t}H $$ t t ¯ H rate. This is achieved via a careful selection of discriminating observables. At the HL-LHC, we find that evidence for tH production at the Standard Model rate can be achieved in the Higgs to diphoton decay channel alone.

SEARCH FOR NEW PHYSICS IN eμX DATA AT THE TEVATRON USING SLEUTH: A QUASI-MODEL-INDEPENDENT SEARCH STRATEGY FOR NEW PHYSICS

2001 ◽  
Vol 16 (supp01b) ◽  
pp. 888-890
Author(s):  
◽  
BRUCE KNUTESON
Keyword(s):  
Standard Model ◽  
Search Strategy ◽  
New Physics ◽  
Beyond The Standard Model ◽  
Final States ◽  
Final State ◽  
The Standard Model ◽  
Model Independent

We present a quasi-model-independent search for physics beyond the standard model. We define final states to be studied, and construct a rule that identifies a set of variables appropriate for any particular final state. A new algorithm ("Sleuth") searches for regions of excess in the space of those variables and quantifies the significance of any detected excess. After demonstrating the sensititvity of the method, we apply it to the semi-inclusive channel eμX collected in ≈108 pb -1 of [Formula: see text] collisions at [Formula: see text] at the DØ experiment at the Fermilab Tevatron. We find no evidence of new high pT physics in this sample.

CAN WE RELATE TIME-REVERSAL VIOLATION TO NEW PHYSICS PROCESSES IN WEAK HADRONIC DECAYS?

2013 ◽  
Vol 22 (03) ◽  
pp. 1330006 ◽  
Author(s):  
Z. J. AJALTOUNI ◽  
E. DI SALVO
Keyword(s):  
Experimental Data ◽  
Cp Violation ◽  
Standard Model ◽  
Time Reversal ◽  
Review Paper ◽  
New Physics ◽  
Hadronic Decays ◽  
Beyond The Standard Model ◽  
Weak Decays ◽  
The Standard Model

This review paper stresses the possible connection between time-reversal violation and new physics processes beyond the standard model. In particular, this violation is proposed as an alternative to CP violation in the search for such unkown processes. Emphasis is put on the weak decays of heavy hadrons, especially beauty ones. Specific methods for extracting useful parameters from experimental data are elaborated in order to test TR symmetry. These methods could be used successfully in the analysis of the LHC data.

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