scholarly journals Production of heavy Higgs bosons and decay into top quarks at the LHC. II. Top-quark polarization and spin correlation effects

2017 ◽  
Vol 95 (9) ◽  
Author(s):  
W. Bernreuther ◽  
P. Galler ◽  
Z.-G. Si ◽  
P. Uwer
Keyword(s):  
Top Quark ◽  
Spin Correlation ◽  
Top Quarks ◽  
Higgs Bosons ◽  
Correlation Effects ◽  
Lhc Ii

scholarly journals Subleading EW corrections and spin-correlation effects in $$t\bar{t}W$$ multi-lepton signatures

2020 ◽  
Vol 80 (9) ◽  
Author(s):  
Rikkert Frederix ◽  
Ioannis Tsinikos
Keyword(s):  
Phase Space ◽  
Cross Section ◽  
Top Quark ◽  
Spin Correlation ◽  
Top Quarks ◽  
Correlation Effects ◽  
Spin Correlations ◽  
Decay Products ◽  
Theoretical Predictions ◽  
The Impact

AbstractRecently a slight tension between data and predictions has been reported in $$t\bar{t}W$$ t t ¯ W production by both the CMS and ATLAS collaborations. We revisit the theoretical predictions for this process, focussing on the following two effects. We disentangle various effects that lead to asymmetries among the leptonic decay products of the (anti-)top quarks and W bosons, for which we find that the spin correlations in the top-quark pair are the dominant source. We also discuss the impact of the large, formally subleading, electroweak corrections to $$t\bar{t}W$$ t t ¯ W production at the LHC. We find that this effect changes the $$t\bar{t}W$$ t t ¯ W cross section significantly in the signature phase-space regions, and should therefore be included differentially in the theory to data comparisons.

SPIN CORRELATION EFFECTS IN THE HADROPRODUCTION AND DECAY OF VERY HEAVY TOP QUARK PAIRS

1989 ◽  
Vol 04 (03) ◽  
pp. 617-625 ◽  
Author(s):  
V. BARGER ◽  
J. OHNEMUS ◽  
R. J. N. PHILLIPS
Keyword(s):  
Top Quark ◽  
Spin Correlation ◽  
Weak Decay ◽  
Tree Level ◽  
Matrix Elements ◽  
Correlation Effects ◽  
Quark Pairs ◽  
Quark Spin ◽  
Dilepton Events ◽  
Top Quark Pairs

Density matrix techniques in the helicity basis allow us to write down explicitly the squared matrix elements for tree-level hadroproduction and weak decay of very heavy top quark pairs, that decay before hadronization. This treatment includes the full effects of quark spin correlation. We illustrate the effects of spin correlation on physical distributions in [Formula: see text] dilepton events, [Formula: see text], [Formula: see text], [Formula: see text], for the case mt =120 GeV at [Formula: see text], the energy of the Tevatron collider. The effects of spin correlation are quantitatively small compared to calculations that ignore them, giving corrections of order 10% or less in the physical distributions studied.

SEARCH FOR CHARGED HIGGS BOSONS IN DECAYS OF PAIR-PRODUCED TOP QUARKS AT DØ

2001 ◽  
Vol 16 (supp01a) ◽  
pp. 395-398
Author(s):  
◽  
PHILLIP GUTIERREZ
Keyword(s):  
Standard Model ◽  
Top Quark ◽  
Top Quarks ◽  
Higgs Bosons ◽  
Full Data ◽  
The Standard Model ◽  
Charged Higgs ◽  
Charged Higgs Bosons

We present a search for t → bH+ in [Formula: see text] candidate events at DØ based on two methods. The first seeks a deficit in signal relative to expectations from the standard model (SM). Such a deficit would imply the presence of a non-SM decay of the top quark. This search involves the full data sample of ≈ 110 pb -1 of [Formula: see text] collisions at [Formula: see text], collected with the DØ detector. The second method looks for charged Higgs decays to τ leptons (and associated neutrinos), and is based on a 62 pb -1 subset of the aforementioned data sample.

scholarly journals Analysis of Top Quark Pair Production Signal from Neutral 2HDM Higgs Bosons at LHC

2018 ◽  
Vol 2018 ◽  
pp. 1-8
Author(s):  
Majid Hashemi ◽  
Mahbobeh Jafarpour
Keyword(s):  
Higgs Boson ◽  
Pair Production ◽  
Top Quark ◽  
Top Quarks ◽  
Higgs Doublet ◽  
Higgs Bosons ◽  
Type I ◽  
Final State ◽  
Doublet Model ◽  
Two Higgs Doublet Model

In this paper, the top quark pair production events are analyzed as a source of neutral Higgs bosons of the two Higgs doublet model type I at LHC. The production mechanism is pp→H/A→tt¯ assuming a fully hadronic final state through t→Wb→jjb. In order to distinguish the signal from the main background which is the standard model tt¯, we benefit from the fact that the top quarks in signal events acquire large Lorentz boost due to the heavy neutral Higgs boson. This feature leads to three collinear jets (a fat jet) which is a discriminating tool for identification of the top quarks from the Higgs boson resonances. Events with two identified top jets are selected and the invariant mass of the top pair is calculated for both signal and background. It is shown that the low tan β region has still some parts which can be covered by this analysis and has not yet been excluded by flavor physics data.

scholarly journals Pulling the Higgs and top needles from the jet stack with feature extended supervised tagging

2021 ◽  
Vol 81 (8) ◽  
Author(s):  
J. A. Aguilar-Saavedra
Keyword(s):  
Higgs Boson ◽  
Top Quark ◽  
Top Quarks ◽  
High Energy ◽  
New Physics ◽  
Higgs Bosons ◽  
Jet Substructure ◽  
Final State ◽  
Charged Leptons ◽  
Energy Frontier

AbstractJet tagging has become an essential tool for new physics searches at the high-energy frontier. For jets that contain energetic charged leptons we introduce Feature Extended Supervised Tagging (FEST) which, in addition to jet substructure, considers the features of the charged lepton within the jet. With this method we build dedicated taggers to discriminate among boosted $$H \rightarrow \ell \nu q {\bar{q}}$$ H → ℓ ν q q ¯ , $$t \rightarrow \ell \nu b$$ t → ℓ ν b , and QCD jets (with $$\ell $$ ℓ an electron or muon). The taggers have an impressive performance, allowing for overall light jet rejection factors of $$10^4-10^5$$ 10 4 - 10 5 , for top quark/Higgs boson efficiencies of 0.5. The taggers are also excellent in the discrimination of Higgs bosons from top quarks and vice versa, for example rejecting top quarks by factors of 100–300 for Higgs boson efficiencies of 0.5. We demonstrate the potential of these taggers to improve the sensitivity to new physics by using as example a search for a new $$Z'$$ Z ′ boson decaying into ZH, in the fully-hadronic final state.

UPDATED BOUNDS ON HIGGS TRIPLET VACUUM EXPECTATION VALUES AND THE TREE-LEVEL ρ PARAMETER FROM RADIATIVE CORRECTIONS

1991 ◽  
Vol 06 (21) ◽  
pp. 1961-1966 ◽  
Author(s):  
THOMAS G. RIZZO
Keyword(s):  
Parity Violation ◽  
Top Quark ◽  
Input Data ◽  
Vacuum Expectation ◽  
Top Quarks ◽  
Higgs Bosons ◽  
Tree Level ◽  
Radiative Corrections ◽  
Expectation Values ◽  
Upper Limits

We obtain 95% C. L. upper limits on the ratio of triplet to doublet vacuum expectation values in two extended electroweak models from radiative corrections. We use as input data from LEP, the Tevatron, the CERN [Formula: see text] colliders, and various low-energy experiments such as atomic parity-violation and deep inelastic scattering. The analysis includes the incorporation of leading two-loop electroweak contributions to ∆r and ρ arising from heavy top quarks and Higgs bosons, the Consoli–Hollik–Jegerlehner resummation technique, and QCD corrections to the hadronic partial widths of the Z using the new value for the (αs/π)3 coefficient. Our limits are found to be only mildly sensitive to the top quark and Higgs boson masses and somewhat stronger than those obtained previously. Our results are then generalized to bounds on the allowed value of the tree-level ρ parameter.

scholarly journals Recent CMS results in top and Higgs physics

2017 ◽  
Vol 32 (29) ◽  
pp. 1730026
Author(s):  
Rebeca Gonzalez Suarez
Keyword(s):  
Higgs Boson ◽  
Standard Model ◽  
Top Quark ◽  
Large Scale ◽  
Top Quarks ◽  
Large Mass ◽  
New Physics ◽  
Higgs Bosons ◽  
Physics Program ◽  
The Standard Model

After the Higgs boson discovery in 2012, the investigation of its properties and compatibility with the Standard Model predictions is central to the physics program of the LHC experiments. Likewise, the study of the top quark is still relevant at the LHC, more than two decades after its discovery at the Tevatron. Top quarks and Higgs bosons are produced at the LHC on a large scale and share a deep connection based on the large mass of the top quark. Both particles provide an excellent laboratory in which to search for new physics: the measurement of their properties tests the foundations of the Standard Model; and they feature prominently in a variety of exotic signals. The coupling of the Higgs boson to the top quark, a fundamental Standard Model parameter, can only be measured directly in processes where the two particles are produced together. The production of a Higgs boson together with one or two top quarks is also sensitive to several exciting new physics effects. A brief overview of the current experimental status of top quark and Higgs boson physics is presented using results from the CMS Collaboration.

scholarly journals ZH production in gluon fusion: two-loop amplitudes with full top quark mass dependence

2021 ◽  
Vol 2021 (3) ◽  
Author(s):  
Long Chen ◽  
Gudrun Heinrich ◽  
Stephen P. Jones ◽  
Matthias Kerner ◽  
Jonas Klappert ◽  
...  
Keyword(s):  
Top Quark ◽  
Quark Mass ◽  
Gluon Fusion ◽  
Top Quarks ◽  
Mass Dependence ◽  
Finite Part ◽  
Top Quark Mass ◽  
Helicity Amplitudes ◽  
Quark Mass Dependence ◽  
Loop Amplitudes

Abstract We present results for the two-loop helicity amplitudes entering the NLO QCD corrections to the production of a Higgs boson in association with a Z -boson in gluon fusion. The two-loop integrals, involving massive top quarks, are calculated numerically. Results for the interference of the finite part of the two-loop amplitudes with the Born amplitude are shown as a function of the two kinematic invariants on which the amplitudes depend.

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