scholarly journals Search for a light pseudoscalar Higgs boson in the boosted μμττ final state in proton-proton collisions at $$ \sqrt{s} $$ = 13 TeV

2020 ◽  
Vol 2020 (8) ◽  
Author(s):  
A. M. Sirunyan ◽  
◽  
A. Tumasyan ◽  
W. Adam ◽  
F. Ambrogi ◽  
...  
Keyword(s):  
Higgs Boson ◽  
Branching Fraction ◽  
Vector Boson ◽  
Mass Difference ◽  
Standard Technique ◽  
Gluon Fusion ◽  
Large Mass ◽  
Proton Collision ◽  
Final State ◽  
Proton Proton

Abstract A search for a light pseudoscalar Higgs boson (a) decaying from the 125 GeV (or a heavier) scalar Higgs boson (H) is performed using the 2016 LHC proton-proton collision data at $$ \sqrt{s} $$ s = 13 TeV, corresponding to an integrated luminosity of 35.9 fb−1, collected by the CMS experiment. The analysis considers gluon fusion and vector boson fusion production of the H, followed by the decay H → aa → μμττ, and considers pseudoscalar masses in the range 3.6 < ma< 21 GeV. Because of the large mass difference between the H and the a bosons and the small masses of the a boson decay products, both the μμ and the ττ pairs have high Lorentz boost and are collimated. The ττ reconstruction efficiency is increased by modifying the standard technique for hadronic τ lepton decay reconstruction to account for a nearby muon. No significant signal is observed. Model-independent limits are set at 95% confidence level, as a function of ma, on the branching fraction (ℬ) for H → aa → μμττ, down to 1.5 (2.0) × 10−4 for mH = 125 (300) GeV. Model-dependent limits on ℬ(H → aa) are set within the context of two Higgs doublets plus singlet models, with the most stringent results obtained for Type-III models. These results extend current LHC searches for heavier a bosons that decay to resolved lepton pairs and provide the first such bounds for an H boson with a mass above 125 GeV.

scholarly journals Reconstruction and identification of boosted di-τ systems in a search for Higgs boson pairs using 13 TeV proton-proton collision data in ATLAS

2020 ◽  
Vol 2020 (11) ◽  
Author(s):  
G. Aad ◽  
◽  
B. Abbott ◽  
D. C. Abbott ◽  
A. Abed Abud ◽  
...  
Keyword(s):  
Higgs Boson ◽  
Hadron Collider ◽  
Gluon Fusion ◽  
Mass Range ◽  
Proton Collision ◽  
Final State ◽  
Proton Proton ◽  
Scalar Resonance ◽  
Proton Proton Collision ◽  
A New Technique

Abstract In this paper, a new technique for reconstructing and identifying hadronically decaying τ+τ− pairs with a large Lorentz boost, referred to as the di-τ tagger, is developed and used for the first time in the ATLAS experiment at the Large Hadron Collider. A benchmark di-τ tagging selection is employed in the search for resonant Higgs boson pair production, where one Higgs boson decays into a boosted $$ b\overline{b} $$ b b ¯ pair and the other into a boosted τ+τ− pair, with two hadronically decaying τ-leptons in the final state. Using 139 fb−1 of proton-proton collision data recorded at a centre-of-mass energy of 13 TeV, the efficiency of the di-τ tagger is determined and the background with quark- or gluon-initiated jets misidentified as di-τ objects is estimated. The search for a heavy, narrow, scalar resonance produced via gluon-gluon fusion and decaying into two Higgs bosons is carried out in the mass range 1–3 TeV using the same dataset. No deviations from the Standard Model predictions are observed, and 95% confidence-level exclusion limits are set on this model.

scholarly journals Evidence for Higgs boson decay to a pair of muons

2021 ◽  
Vol 2021 (1) ◽  
Author(s):  
A. M. Sirunyan ◽  
◽  
A. Tumasyan ◽  
W. Adam ◽  
T. Bergauer ◽  
...  
Keyword(s):  
Higgs Boson ◽  
Top Quark ◽  
Vector Boson ◽  
Gluon Fusion ◽  
Measured Signal ◽  
Proton Collision ◽  
Proton Proton ◽  
Back Ground ◽  
Proton Proton Collision ◽  
8 Tev

Abstract Evidence for Higgs boson decay to a pair of muons is presented. This result combines searches in four exclusive categories targeting the production of the Higgs boson via gluon fusion, via vector boson fusion, in association with a vector boson, and in association with a top quark-antiquark pair. The analysis is performed using proton-proton collision data at $$ \sqrt{s} $$ s = 13 TeV, corresponding to an integrated luminosity of 137 fb−1, recorded by the CMS experiment at the CERN LHC. An excess of events over the back- ground expectation is observed in data with a significance of 3.0 standard deviations, where the expectation for the standard model (SM) Higgs boson with mass of 125.38 GeV is 2.5. The combination of this result with that from data recorded at $$ \sqrt{s} $$ s = 7 and 8 TeV, corresponding to integrated luminosities of 5.1 and 19.7 fb−1, respectively, increases both the expected and observed significances by 1%. The measured signal strength, relative to the SM prediction, is $$ {1.19}_{-0.39}^{+0.40}{\left(\mathrm{stat}\right)}_{-0.14}^{+0.15}\left(\mathrm{syst}\right) $$ 1.19 − 0.39 + 0.40 stat − 0.14 + 0.15 syst . This result constitutes the first evidence for the decay of the Higgs boson to second generation fermions and is the most precise measurement of the Higgs boson coupling to muons reported to date.

scholarly journals Search for the doubly charmed baryon $$\Xi_{cc}^+$$

2019 ◽  
Vol 63 (2) ◽  
Author(s):  
R. Aaij ◽  
◽  
C. Abellán Beteta ◽  
T. Ackernley ◽  
B. Adeva ◽  
...  
Keyword(s):  
Production Cross ◽  
Branching Fraction ◽  
Mass Range ◽  
Proton Collision ◽  
Final State ◽  
Momentum Range ◽  
Proton Proton ◽  
Charmed Baryon ◽  
Upper Limits ◽  
Lhcb Detector

AbstractA search for the doubly charmed baryon $$\Xi_{cc}^+$$Ξcc+ is performed through its decay to the $$\Lambda_c^ + {K^ -}{\pi ^ +}$$Λc+K−π+ final state, using proton-proton collision data collected with the LHCb detector at centre-of-mass energies of 7, 8 and 13 TeV. The data correspond to a total integrated luminosity of 9 fb−1. No significant signal is observed in the mass range from 3.4 to 3.8 GeV/c2. Upper limits are set at 95% credibility level on the ratio of the $$\Xi_{cc}^+$$Ξcc+ production cross-section times the branching fraction to that of $$\Lambda_c^ + $$Λc+ and $$\Xi_{cc}^{+ +}$$Ξcc++ baryons. The limits are determined as functions of the $$\Xi_{cc}^+$$Ξcc+ mass for different lifetime hypotheses, in the rapidity range from 2.0 to 4.5 and the transverse momentum range from 4 to 15 GeV/c.

scholarly journals Systematic study of diphoton resonance at 750 GeV from sgoldstino

2016 ◽  
Vol 31 (26) ◽  
pp. 1650151 ◽  
Author(s):  
Ran Ding ◽  
Yizhou Fan ◽  
Li Huang ◽  
Chuang Li ◽  
Tianjun Li ◽  
...  
Keyword(s):  
Decay Width ◽  
Cross Section ◽  
Production Cross Section ◽  
Production Cross ◽  
Vector Boson ◽  
Mass Difference ◽  
Hadron Collider ◽  
Gluon Fusion ◽  
Large Mass ◽  
Decay Length

The ATLAS and CMS Collaborations of the Large Hadron Collider (LHC) have reported an excess of events in diphoton channel with invariant mass of about 750 GeV. With low energy supersymmetry breaking, we systematically consider the sgoldstino scalar S as the new resonance, which is a linear combination of the CP-even scalar [Formula: see text] and CP-odd pseudoscalar [Formula: see text]. Because we show that [Formula: see text] and [Formula: see text] can be degenerated or have large mass splitting, we consider two cases for all the following three scenarios: (1) Single resonance, [Formula: see text] is the 750 GeV resonance decays to a pair of 1 GeV pseudoscalar [Formula: see text] with suitable decay length, these two [Formula: see text] decay into collimated pair of photons which cannot be distinguished at the LHC and may appear as diphotons instead of four photons. (2) Twin resonances, [Formula: see text] with a mass difference of about 40 GeV and both [Formula: see text] and [Formula: see text] decay into diphoton pairs. For productions, we consider three scenarios: (I) vector-boson fusion; (II) gluon–gluon fusion; (III) [Formula: see text] pair production. In all these scenarios with two kinds of resonances, we find the parameter space that satisfies the diphoton production cross-section from 3 to 13 fb and all the other experimental constraints. And we address the decay width as well. In particular, in the third scenario, we observe that the production cross-section is small but the decay width of [Formula: see text] or [Formula: see text] can be from 40 to 60 GeV. Even if the 750 GeV diphoton excesses were not confirmed by the ATLAS and CMS experiments, we point out that our proposal can be used to explain the current and future diphoton excesses.

scholarly journals Search for a heavy vector resonance decaying to a $${\mathrm{Z}}_{\mathrm{}}^{\mathrm{}}$$  boson and a Higgs boson in proton-proton collisions at $$\sqrt{s} = 13\,\text {Te}\text {V} $$

2021 ◽  
Vol 81 (8) ◽  
Author(s):  
A. M. Sirunyan ◽  
A. Tumasyan ◽  
W. Adam ◽  
T. Bergauer ◽  
M. Dragicevic ◽  
...  
Keyword(s):  
Higgs Boson ◽  
Standard Model ◽  
Branching Fraction ◽  
Vector Boson ◽  
Hadronic Decays ◽  
Vector Resonance ◽  
Proton Proton ◽  
Leptonic Decays ◽  
Upper Limits ◽  
Proton Proton Collisions

AbstractA search is presented for a heavy vector resonance decaying into a $${\mathrm{Z}}_{\mathrm{}}^{\mathrm{}}$$ Z boson and the standard model Higgs boson, where the $${\mathrm{Z}}_{\mathrm{}}^{\mathrm{}}$$ Z boson is identified through its leptonic decays to electrons, muons, or neutrinos, and the Higgs boson is identified through its hadronic decays. The search is performed in a Lorentz-boosted regime and is based on data collected from 2016 to 2018 at the CERN LHC, corresponding to an integrated luminosity of 137$$\,\text {fb}^{-1}$$ fb - 1 . Upper limits are derived on the production of a narrow heavy resonance $${\mathrm{{{\mathrm{Z}}_{\mathrm{}}^{\mathrm{}}}}}_{\mathrm{}}^{\mathrm{\prime }}$$ Z ′ , and a mass below 3.5 and 3.7$$\,\text {Te}\text {V}$$ Te is excluded at 95% confidence level in models where the heavy vector boson couples predominantly to fermions and to bosons, respectively. These are the most stringent limits placed on the Heavy Vector Triplet $${\mathrm{{{\mathrm{Z}}_{\mathrm{}}^{\mathrm{}}}}}_{\mathrm{}}^{\mathrm{\prime }}$$ Z ′ model to date. If the heavy vector boson couples exclusively to standard model bosons, upper limits on the product of the cross section and branching fraction are set between 23 and 0.3$$\,\text {fb}$$ fb for a $${\mathrm{{{\mathrm{Z}}_{\mathrm{}}^{\mathrm{}}}}}_{\mathrm{}}^{\mathrm{\prime }}$$ Z ′ mass between 0.8 and 4.6$$\,\text {Te}\text {V}$$ Te , respectively. This is the first limit set on a heavy vector boson coupling exclusively to standard model bosons in its production and decay.

Review of combined measurements of Higgs boson production and decay using up to 80 fb−1 of proton–proton collision data at s = 13 TeV collected with the ATLAS experiment

2020 ◽  
pp. 2030023
Author(s):  
Hongtao Yang
Keyword(s):  
Higgs Boson ◽  
Standard Model ◽  
Vector Boson ◽  
Proton Collision ◽  
Boson Production ◽  
Proton Proton ◽  
Associated Production ◽  
The Standard Model ◽  
Proton Proton Collision ◽  
Combined Measurements

The combined measurements of Higgs boson production and decay are performed based on up to 80 fb[Formula: see text] of proton–proton collision data collected at [Formula: see text] = 13 TeV by the ATLAS detector. The overall signal strength, defined as measured signal yield divided by the Standard Model prediction, is [Formula: see text]. The inclusive and differential cross-sections of gluon–gluon fusion, vector-boson fusion, associated production with vector boson, and associated production with top quarks processes are also measured. The measurements are interpreted with leading-order motivated coupling strength modifiers. No significant deviations from the Standard Model predictions are observed.

scholarly journals Impact of additional bosons on the exploration of the Higgs boson at the LHC

2017 ◽  
Vol 32 (34) ◽  
pp. 1746010 ◽  
Author(s):  
Yaquan Fang ◽  
Mukesh Kumar ◽  
Bruce Mellado ◽  
Yu Zhang ◽  
Maosen Zhu
Keyword(s):  
Higgs Boson ◽  
Production Cross ◽  
Vector Boson ◽  
New Production ◽  
Final State ◽  
Proton Proton ◽  
Text Production ◽  
Proton Data ◽  
Inclusive Rate ◽  
The Impact

The LHC is making strides in the exploration of the properties of the newly discovered Higgs boson, [Formula: see text]. In Refs. 7–9 the compatibility of the proton–proton data reported in the Run I period with the presence of a heavy scalar, [Formula: see text], with a mass around 270 GeV and its implications were explored. This boson would decay predominantly to [Formula: see text], where [Formula: see text], is a lighter scalar boson. The production cross-section of [Formula: see text] is considerable and it would significantly affect the inclusive rate of [Formula: see text]. The contamination from this new production mechanism would depend strongly on the final state used to measure the rate of [Formula: see text]. The contamination in the rate measurement of [Formula: see text], [Formula: see text], [Formula: see text] is estimated to be small. This statement does not depend strongly on assumptions made on the decay of [Formula: see text]. The impact on other channels related to the search of Vector Boson Fusion and [Formula: see text] production with the diphoton decay is evaluated, where the dependence on assumption on the decay of [Formula: see text] is expected to be significant.

scholarly journals Search for dark matter in events with missing transverse momentum and a Higgs boson decaying into two photons in pp collisions at $$ \sqrt{s} $$ = 13 TeV with the ATLAS detector

2021 ◽  
Vol 2021 (10) ◽  
Author(s):  
◽  
G. Aad ◽  
B. Abbott ◽  
D. C. Abbott ◽  
A. Abed Abud ◽  
...  
Keyword(s):  
Dark Matter ◽  
Higgs Boson ◽  
Transverse Momentum ◽  
Atlas Detector ◽  
Proton Collision ◽  
Final State ◽  
Proton Proton ◽  
Missing Transverse Momentum ◽  
Higgs Boson Decaying ◽  
Proton Proton Collision

Abstract A search for dark-matter particles in events with large missing transverse momentum and a Higgs boson candidate decaying into two photons is reported. The search uses 139 fb−1 of proton-proton collision data collected at $$ \sqrt{s} $$ s = 13 TeV with the ATLAS detector at the CERN LHC between 2015 and 2018. No significant excess of events over the Standard Model predictions is observed. The results are interpreted by extracting limits on three simplified models that include either vector or pseudoscalar mediators and predict a final state with a pair of dark-matter candidates and a Higgs boson decaying into two photons.

scholarly journals Search for R-parity violating supersymmetry and quantum blackholes in eμ final state in CMS

2018 ◽  
Vol 182 ◽  
pp. 03011
Author(s):  
Swagata Mukherjee
Keyword(s):  
Mass Spectrum ◽  
Extra Dimensions ◽  
Branching Fraction ◽  
Invariant Mass Spectrum ◽  
Proton Collision ◽  
Beyond The Standard Model ◽  
Final State ◽  
Proton Proton ◽  
Upper Limits ◽  
Flavour Violation

A search for narrow resonances decaying to an electron and a muon is performed using an integrated luminosity of 2.7 fb-1 of 13 TeV proton-proton collision data recorded with the CMS detector at the LHC. The eμ mass spectrum is also investigated for non-resonant contributions from the production of quantum black holes (QBH). With no evidence for physics beyond the standard model in the invariant mass spectrum of selected eμ pairs, upper limits are set at 95% confidence level on the product of cross section and branching fraction for signals arising in theories with charged lepton flavour violation. In the search for narrow resonances, the resonant production of a π sneutrino in R-parity violating supersymmetry is considered. The π sneutrino is excluded for masses below 1.0 TeV for couplings λ132 = λ231 = λ'311 = 0:01 and below 3.3 TeV for λ132 = λ231 = λ'311 = 0:2. In a framework of TeV-scale quantum gravity, for models that invoke extra dimensions, the observed exclusion limits for the threshold mass of QBH production range from 2.5 TeV for one extra dimension to 4.5 TeV for six extra dimensions.

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