skip to main content

Explore Research Products in the NSF-PAR

  • NSF Public Access
  • Search Results
  • On the sensitivity reach of $$\textrm{LQ}$$ production with preferential couplings to third generation fermions at the LHC
Title: On the sensitivity reach of $$\textrm{LQ}$$ production with preferential couplings to third generation fermions at the LHC
Abstract

Leptoquarks ($$\textrm{LQ}$$LQs) are hypothetical particles that appear in various extensions of the Standard Model (SM), that can explain observed differences between SM theory predictions and experimental results. The production of these particles has been widely studied at various experiments, most recently at the Large Hadron Collider (LHC), and stringent bounds have been placed on their masses and couplings, assuming the simplest beyond-SM (BSM) hypotheses. However, the limits are significantly weaker for$$\textrm{LQ}$$LQmodels with family non-universal couplings containing enhanced couplings to third-generation fermions. We present a new study on the production of a$$\textrm{LQ}$$LQat the LHC, with preferential couplings to third-generation fermions, considering proton-proton collisions at$$\sqrt{s} = 13 \, \textrm{TeV}$$s=13TeVand$$\sqrt{s} = 13.6 \, \textrm{TeV}$$s=13.6TeV. Such a hypothesis is well motivated theoretically and it can explain the recent anomalies in the precision measurements of$$\textrm{B}$$B-meson decay rates, specifically the$$R_{D^{(*)}}$$RD(∗)ratios. Under a simplified model where the$$\textrm{LQ}$$LQmasses and couplings are free parameters, we focus on cases where the$$\textrm{LQ}$$LQdecays to a$$\tau $$τlepton and a$$\textrm{b}$$bquark, and study how the results are affected by different assumptions about chiral currents and interference effects with other BSM processes with the same final states, such as diagrams with a heavy vector boson,$$\textrm{Z}^{\prime }$$Z′. The analysis is performed using machine learning techniques, resulting in an increased discovery reach at the LHC, allowing us to probe new physics phase space which addresses the$$\textrm{B}$$B-meson anomalies, for$$\textrm{LQ}$$LQmasses up to$$5.00\, \textrm{TeV}$$5.00TeV, for the high luminosity LHC scenario.

  more » « less
Award ID(s):
1945366
NSF-PAR ID:
10473618
Author(s) / Creator(s):
; ; ; ;
Publisher / Repository:
Springer Science + Business Media
Date Published:
Journal Name:
The European Physical Journal C
Volume:
83
Issue:
11
ISSN:
1434-6052
Format(s):
Medium: X
Sponsoring Org:
National Science Foundation
More Like this
  1. ; ; ; ; ; ; ; ; ; ; et al ( , The European Physical Journal C)
    Abstract

    A search is reported for pairs of light Higgs bosons ($${\textrm{H}} _1$$H1) produced in supersymmetric cascade decays in final states with small missing transverse momentum. A data set of LHC$$\hbox {pp}$$ppcollisions collected with the CMS detector at$$\sqrt{s}=13\,\text {TeV} $$s=13TeVand corresponding to an integrated luminosity of 138$$\,\text {fb}^{-1}$$fb-1is used. The search targets events where both$${\textrm{H}} _1$$H1bosons decay into Equation missing<#comment/>pairs that are reconstructed as large-radius jets using substructure techniques. No evidence is found for an excess of events beyond the background expectations of the standard model (SM). Results from the search are interpreted in the next-to-minimal supersymmetric extension of the SM, where a “singlino” of small mass leads to squark and gluino cascade decays that can predominantly end in a highly Lorentz-boosted singlet-like$${\textrm{H}} _1$$H1and a singlino-like neutralino of small transverse momentum. Upper limits are set on the product of the squark or gluino pair production cross section and the square of the Equation missing<#comment/>branching fraction of the$${\textrm{H}} _1$$H1in a benchmark model containing almost mass-degenerate gluinos and light-flavour squarks. Under the assumption of an SM-like Equation missing<#comment/>branching fraction,$${\textrm{H}} _1$$H1bosons with masses in the range 40–120$$\,\text {GeV}$$GeVarising from the decays of squarks or gluinos with a mass of 1200–2500$$\,\text {GeV}$$GeVare excluded at 95% confidence level.

     
    more » « less
  2. ; ; ; ; ; ; ; ; ; ; et al ( , The European Physical Journal C)
    Abstract

    A search for decays to invisible particles of Higgs bosons produced in association with a top-antitop quark pair or a vector boson, which both decay to a fully hadronic final state, has been performed using proton-proton collision data collected at$${\sqrt{s}=13\,\text {Te}\hspace{-.08em}\text {V}}$$s=13TeVby the CMS experiment at the LHC, corresponding to an integrated luminosity of 138$$\,\text {fb}^{-1}$$fb-1. The 95% confidence level upper limit set on the branching fraction of the 125$$\,\text {Ge}\hspace{-.08em}\text {V}$$GeVHiggs boson to invisible particles,$${\mathcal {B}({\textrm{H}} \rightarrow \text {inv})}$$B(H→inv), is 0.54 (0.39 expected), assuming standard model production cross sections. The results of this analysis are combined with previous$${\mathcal {B}({\textrm{H}} \rightarrow \text {inv})}$$B(H→inv)searches carried out at$${\sqrt{s}=7}$$s=7, 8, and 13$$\,\text {Te}\hspace{-.08em}\text {V}$$TeVin complementary production modes. The combined upper limit at 95% confidence level on$${\mathcal {B}({\textrm{H}} \rightarrow \text {inv})}$$B(H→inv)is 0.15 (0.08 expected).

     
    more » « less
  3. ; ; ; ; ; ; ; ; ; ; et al ( , The European Physical Journal C)
    Abstract

    This paper reports a search for Higgs boson pair (hh) production in association with a vector boson ($$W\; {\text {o}r}\; Z$$WorZ) using 139 fb$$^{-1}$$-1of proton–proton collision data at$$\sqrt{s}=13\,\text {TeV}$$s=13TeVrecorded with the ATLAS detector at the Large Hadron Collider. The search is performed in final states in which the vector boson decays leptonically ($$W\rightarrow \ell \nu ,\, Z\rightarrow \ell \ell ,\nu \nu $$W→ℓν,Z→ℓℓ,ννwith$$\ell =e, \mu $$ℓ=e,μ) and the Higgs bosons each decay into a pair ofb-quarks. It targetsVhhsignals from both non-resonanthhproduction, present in the Standard Model (SM), and resonanthhproduction, as predicted in some SM extensions. A 95% confidence-level upper limit of 183 (87) times the SM cross-section is observed (expected) for non-resonantVhhproduction when assuming the kinematics are as expected in the SM. Constraints are also placed on Higgs boson coupling modifiers. For the resonant search, upper limits on the production cross-sections are derived for two specific models: one is the production of a vector boson along with a neutral heavy scalar resonanceH, in the mass range 260–1000 GeV, that decays intohh, and the other is the production of a heavier neutral pseudoscalar resonanceAthat decays into aZboson andHboson, where theAboson mass is 360–800 GeV and theHboson mass is 260–400 GeV. Constraints are also derived in the parameter space of two-Higgs-doublet models.

     
    more » « less
  4. ; ; ; ; ; ; ; ; ; ; et al ( , The European Physical Journal C)
    Abstract

    A search for pair-produced vector-like quarks using events with exactly one lepton (eor$$\mu $$μ), at least four jets including at least oneb-tagged jet, and large missing transverse momentum is presented. Data from proton–proton collisions at a centre-of-mass energy of$$\sqrt{s}=$$s=13 $$\text {TeV}$$TeV, recorded by the ATLAS detector at the LHC from 2015 to 2018 and corresponding to an integrated luminosity of 139 fb$$^{-1}$$-1, are analysed. Vector-like partnersTandBof the top and bottom quarks are considered, as is a vector-likeXwith charge$$+5/3$$+5/3, assuming their decay into aW,Z, or Higgs boson and a third-generation quark. No significant deviations from the Standard Model expectation are observed. Upper limits on the production cross-section ofTandBquark pairs as a function of their mass are derived for various decay branching ratio scenarios. The strongest lower limits on the masses are 1.59 $$\text {TeV}$$TeVassuming mass-degenerate vector-like quarks and branching ratios corresponding to the weak-isospin doublet model, and 1.47 $$\text {TeV}$$TeV(1.46 $$\text {TeV}$$TeV) for exclusive$$T \rightarrow Zt$$T→Zt($$B/X \rightarrow Wt$$B/X→Wt) decays. In addition, lower limits on theTandBquark masses are derived for all possible branching ratios.

     
    more » « less
  5. ; ; ; ; ; ; ; ; ; ; et al ( , Journal of High Energy Physics)
    A<sc>bstract</sc>

    Three searches are presented for signatures of physics beyond the standard model (SM) inττfinal states in proton-proton collisions at the LHC, using a data sample collected with the CMS detector at$$ \sqrt{s} $$s= 13 TeV, corresponding to an integrated luminosity of 138 fb−1. Upper limits at 95% confidence level (CL) are set on the products of the branching fraction for the decay intoτleptons and the cross sections for the production of a new bosonϕ, in addition to the H(125) boson, via gluon fusion (ggϕ) or in association with b quarks, ranging from$$ \mathcal{O} $$O(10 pb) for a mass of 60 GeV to 0.3 fb for a mass of 3.5 TeV each. The data reveal two excesses for ggϕproduction with localp-values equivalent to about three standard deviations atmϕ= 0.1 and 1.2 TeV. In a search fort-channel exchange of a vector leptoquark U1, 95% CL upper limits are set on the dimensionless U1leptoquark coupling to quarks andτleptons ranging from 1 for a mass of 1 TeV to 6 for a mass of 5 TeV, depending on the scenario. In the interpretations of the$$ {M}_{\textrm{h}}^{125} $$Mh125and$$ {M}_{\textrm{h},\textrm{EFT}}^{125} $$Mh,EFT125minimal supersymmetric SM benchmark scenarios, additional Higgs bosons with masses below 350 GeV are excluded at 95% CL.

     
    more » « less
  • Citation Formats
  • MLA
  • APA
  • Chicago
  • BibTeX
  • Save / Share this Record
  • Send to Email