LHCb Collaboration(Aaij, R. et al), Jashal, B. K., Martinez-Vidal, F., Oyanguren, A., Remon Alepuz, C., & Ruiz Vidal, J. (2022). Measurement of chi(c1) (3872) production in proton-proton collisions at root s=8 and 13 TeV. J. High Energy Phys., 01(1), 131–27pp.
Abstract: The production cross-section of the chi(c1)(3872) state relative to the psi(2S) meson is measured using proton-proton collision data collected with the LHCb experiment at centre-of-mass energies of root s = 8 and 13 TeV, corresponding to integrated luminosities of 2.0 and 5.4 fb(-1), respectively. The two mesons are reconstructed in the J/psi pi(+) pi(-) final state. The ratios of the prompt and nonprompt chi(c1)(3872) to psi(2S) production cross-sections are measured as a function of transverse momentum, p(T), and rapidity, y, of the chi(c1)(3872) and psi(2S) states, in the kinematic range 4 < p(T) < 20 GeV/c and 2.0 < y < 4.5. The prompt ratio is found to increase with pT , independently of y. For the prompt component, the double ratio of the chi(c1)(3872) and psi(2S) production cross-sections between 13 and 8 TeV is observed to be consistent with unity, independent of p(T) and centre-of-mass energy.
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LHCb Collaboration(Aaij, R. et al), Oyanguren, A., & Ruiz Valls, P. (2013). Limits on neutral Higgs boson production in the forward region in pp collisions at root s=7 TeV. J. High Energy Phys., 05(5), 132–13pp.
Abstract: Limits on the cross-section times branching fraction for neutral Higgs bosons, produced in p p collisions at root s = 7 TeV, and decaying to two tau leptons with pseudorapidities between 2.0 and 4.5, are presented. The result is based on a dataset, corresponding to an integrated luminosity of 1.0 fb(-1), collected with the LHCb detector. Candidates are identified by reconstructing final states with two muons, a muon and an electron, a muon and a hadron, or an electron and a hadron. A model independent upper limit at the 95% confidence level is set on a neutral Higgs boson cross-section times branching fraction. It varies from 8.6 pb for a Higgs boson mass of 90 GeV to 0.7 pb for a Higgs boson mass of 250 GeV, and is compared to the Standard Model expectation. An upper limit on tan beta in the Minimal Supersymmetric Model is set in the m(h0)(max) scenario. It ranges from 34 for a CP-odd Higgs boson mass of 90 GeV to 70 for a pseudo-scalar Higgs boson mass of 140 GeV.
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LHCb Collaboration(Aaij, R. et al), Martinez-Vidal, F., Oyanguren, A., Ruiz Valls, P., & Sanchez Mayordomo, C. (2016). Observation of Lambda(0)(b) -> psi (2S)pK(-) and Lambda(0)(b) -> J/psi pi(+)pi(-)pK(-) decays and a measurement of the A(b)(0) baryon mass. J. High Energy Phys., 05(5), 132–22pp.
Abstract: The decays Lambda(0)(b) -> psi(2S)pK(-) and Lambda(0)(b) -> J/psi pi(+)pi(-)pK(-) are observed in a data sample corresponding to an integrated luminosity of 3 fb(-1), collected in proton-proton collisions at 7 and 8 TeV centre-of-mass energies by the LHCb detector. The psi(2S) mesons are reconstructed through the decay modes psi(2S) -> mu(+)mu(-) and psi(2S) -> J/psi pi(+)pi(-) The branching fractions relative to that of Lambda(0)(b) -> J/psi pk(-) are measured to be [GRAPHICS] where the first uncertainties are statistical, the second are systematic and the third is related to the knowledge of J/psi and psi(2S) branching fractions. The mass of the Ai baryon is measured to be M(Lambda(0)(b)) = 5619.65 +/- 0.17 0.17 MeV/c(2), where the uncertainties are statistical and systematic.
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ATLAS Collaboration(Aaboud, M. et al), Alvarez Piqueras, D., Barranco Navarro, L., Cabrera Urban, S., Castillo Gimenez, V., Cerda Alberich, L., et al. (2017). Measurement of inclusive and differential cross sections in the H -> ZZ* -> 4l decay channel in pp collisions at root s=13 TeV with the ATLAS detector. J. High Energy Phys., 10(10), 132–49pp.
Abstract: Inclusive and differential fiducial cross sections of Higgs boson production in proton-proton collisions are measured in the H -> Z Z* -> 4l decay channel. The proton-proton collision data were produced at the Large Hadron Collider at a centre-of-mass energy of 13 TeV and recorded by the ATLAS detector in 2015 and 2016, corresponding to an integrated luminosity of 36.1 fb(-1). The inclusive fiducial cross section in the H -> Z Z* -> 4l decay channel is measured to be 3.62 +/- 0.50 (stat) (+0.25)(-0.20) (sys) fb, in agreement with the Standard Model prediction of 2.91 +/- 0.13 fb. The cross section is also extrapolated to the total phase space including all Standard Model Higgs boson decays. Several differential fiducial cross sections are measured for observables sensitive to the Higgs boson production and decay, including kinematic distributions of jets produced in association with the Higgs boson. Good agreement is found between data and Standard Model predictions. The results are used to put constraints on anomalous Higgs boson interactions with Standard Model particles, using the pseudo-observable extension to the kappa-framework.
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LHCb Collaboration(Aaij, R. et al), Martinez-Vidal, F., Oyanguren, A., Ruiz Valls, P., & Sanchez Mayordomo, C. (2014). Differential branching fractions and isospin asymmetries of B -> K ((*)) μ(+) μ(-) decays. J. High Energy Phys., 06(6), 133–22pp.
Abstract: The isospin asymmetries of B -> K μ(+) μ(-) and B -> K (*) μ(+) μ(-) decays and the partial branching fractions of the B (0) -> K (0) μ(+) μ(-), B (+) -> K (+) μ(+) μ(-) and B (+) -> K (*+) μ(+) μ(-) decays are measured as functions of the dimuon mass squared, q (2). The data used correspond to an integrated luminosity of 3 fb(-1) from proton-proton collisions collected with the LHCb detector at centre-of-mass energies of 7 TeV and 8 TeV in 2011 and 2012, respectively. The isospin asymmetries are both consistent with the Standard Model expectations. The three measured branching fractions favour lower values than their respective theoretical predictions, however they are all individually consistent with the Standard Model.
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LHCb Collaboration(Aaij, R. et al), Martinez-Vidal, F., Oyanguren, A., Ruiz Valls, P., & Sanchez Mayordomo, C. (2016). Study of D-(*())(+)(sJ) mesons decaying to D*K-+(S)0 and D*K-0(+) final states. J. High Energy Phys., 02(2), 133–26pp.
Abstract: A search is performed for D-sJ(()*()+) mesons in the reactions pp -> D*(+KSX)-X-0 and pp -> D*(K+X)-K-0 using data collected at centre-of-mass energies of 7 and 8 TeV with the LHCb detector. For the D*K-+(S)0 final state, the decays D*(+) -> D-0 pi(+) with D-0 -> K-pi(+) and D-0 -> K-pi(+)pi(+)pi(-) are used. For D*K-0(+), the decay D*(0) -> D-0 pi(0) with D-0 -> K-pi(+) is used. A prominent D-s1(2536)(+) signal is observed in both D*K-+(S)0 and D*K-0(+) final states. The resonances D*(s1)(2700)(+) and D*(s3)(2860)(+) are also observed, yielding information on their properties, including spin-parity assignments. The decay D*(s2)(2573)(+) -> D*(+) K-S(0) is observed for the first time, at a significance of 6.9 sigma, and its branching fraction relative to the D*(s2)(2573)(+) -> (D+KS0) decay mode is measured.
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ATLAS Collaboration(Aad, G. et al), Amos, K. R., Aparisi Pozo, J. A., Bailey, A. J., Bouchhar, N., Cabrera Urban, S., et al. (2023). Search for dark photons from Higgs boson decays via ZH production with a photon plus missing transverse momentum signature from pp collisions at √s=13 TeV with the ATLAS detector. J. High Energy Phys., 07(7), 133–51pp.
Abstract: This paper describes a search for dark photons (gamma(d)) in proton-proton collisions at root s = 13TeV at the Large Hadron Collider (LHC). The dark photons are searched for in the decay of Higgs bosons ( H -> gamma gamma(d)) produced through the ZH production mode. The transverse mass of the system, made of the photon and the missing transverse momentum from the non-interacting gamma(d), presents a distinctive signature as it peaks near the Higgs boson mass. The results presented use the total Run-2 integrated luminosity of 139 fb(-1) recorded by the ATLAS detector at the LHC. The dominant reducible background processes are estimated using data-driven techniques. A Boosted Decision Tree technique is adopted to enhance the sensitivity of the search. As no excess is observed with respect to the Standard Model prediction, an observed (expected) upper limit on the branching ratio BR( H -> gamma gamma(d)) of 2.28% (2.82(-0.84%)(+1.33)) is set at 95% CL for massless gamma(d). For massive dark photons up to 40 GeV, the observed (expected) upper limits on BR( H -> gamma gamma(d)) at 95% confidence level is found within the [2.19,2.52]% ([2.71,3.11]%) range.
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ATLAS Collaboration(Aad, G. et al), Alvarez Piqueras, D., Cabrera Urban, S., Castillo Gimenez, V., Costa, M. J., Fernandez Martinez, P., et al. (2015). Summary of the ATLAS experiment's sensitivity to supersymmetry after LHC Run 1-interpreted in the phenomenological MSSM. J. High Energy Phys., 10(10), 134–76pp.
Abstract: A summary of the constraints from the ATLAS experiment on R-parity-conserving supersymmetry is presented. Results from 22 separate ATLAS searches are considered, each based on analysis of up to 20.3 fb(-1) of proton-proton collision data at centre-of-mass energies of root s = 7 and 8TeV at the Large Hadron Collider. The results are interpreted in the context of the 19-parameter phenomenological minimal supersymmetric standard model, in which the lightest supersymmetric particle is a neutralino, taking into account constraints from previous precision electroweak and flavour measurements as well as from dark matter related measurements. The results are presented in terms of constraints on supersymmetric particle masses and are compared to limits from simplified models. The impact of ATLAS searches on parameters such as the dark matter relic density, the couplings of the observed Higgs boson, and the degree of electroweak fine-tuning is also shown. Spectra for surviving supersymmetry model points with low fine-tunings are presented.
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LHCb Collaboration(Aaij, R. et al), Garcia Martin, L. M., Henry, L., Martinez-Vidal, F., Oyanguren, A., Remon Alepuz, C., et al. (2018). Measurement of Upsilon production in pp collisions at root s=13 TeV. J. High Energy Phys., 07(7), 134–27pp.
Abstract: The production cross-sections of Upsilon(1S), Upsilon(2S) and Upsilon(3S) mesons in proton-proton collisions at root s = 13 TeV are measured with a data sample corresponding to an integrated luminosity of 277 +/- 11 pb(-1) recorded by the LHCb experiment in 2015. The Upsilon mesons are reconstructed in the decay mode Upsilon -> mu(+)mu(-). The differential production cross-sections times the dimuon branching fractions are measured as a function of the Upsilon transverse momentum, p(T) , and rapidity, y, over the range 0 < p(T) < 30 GeV/c and 2.0 < y < 4.5. The ratios of the cross-sections with respect to the LHCb measurement at root s = 8 TeV are also determined. The measurements are compared with theoretical predictions based on NRQCD.
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LHCb Collaboration(Aaij, R. et al), Garcia Martin, L. M., Martinez-Vidal, F., Oyanguren, A., Remon Alepuz, C., Ruiz Valls, P., et al. (2016). Measurement of the forward Z boson production cross-section in pp collisions at root s=13 TeV. J. High Energy Phys., 09(9), 136–33pp.
Abstract: A measurement of the production cross-section of Z bosons in pp collisions at root s=13 TeV is presented using dimuon and dielectron final states in LHCb data. The cross-section is measured for leptons with pseudorapidities in the range 2.0 < eta < 4.5, transverse momenta pT > 20 GeV and dilepton invariant mass in the range 60 < m(ll) < 120 GeV. The integrated cross-section from averaging the two final states is sigma(ll)(Z) = 194.3+/-0.9+/-3.3+/-7.6 pb, where the first uncertainty is statistical, the second is due to systematic effects, and the third is due to the luminosity determination. In addition, differential cross-sections are measured as functions of the Z boson rapidity, transverse momentum and the angular variable phi(eta)*.
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