ATLAS Collaboration(Aad, G. et al), Cabrera Urban, S., Castillo Gimenez, V., Costa, M. J., Fassi, F., Ferrer, A., et al. (2014). Measurement of the production cross-section of psi(2S) -> J/psi(-> mu(+)mu(-))pi(+) pi(-) in pp collisions at root s=7 TeV at ATLAS. J. High Energy Phys., 09(9), 079–49pp.
Abstract: The prompt and non-prompt production cross-sections for psi(2S) mesons are measured using 2.1 fb(-1) of pp collision data at a centre-of-mass energy of 7TeV recorded by the ATLAS experiment at the LHC. The measurement exploits the psi(2S) --> J/psi(--> mu(+)mu(-)) pi(+)pi(-) decay mode, and probes psi(2S) mesons with transverse momenta in the range 10 <= p(T) < 100 GeV and rapidity |y| < 2.0. The results are compared to other measurements of psi(2S) production at the LHC and to various theoretical models for prompt and non-prompt quarkonium production.
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ATLAS Collaboration(Aad, G. et al), Cabrera Urban, S., Castillo Gimenez, V., Costa, M. J., Fassi, F., Ferrer, A., et al. (2014). Measurement of the production of a W boson in association with a charm quark in pp collisions at root s=7 TeV with the ATLAS detector. J. High Energy Phys., 05(5), 068–67pp.
Abstract: The production of a W boson in association with a single charm quark is studied using 4.6 fb(-1) of pp collision data at root s = 7 TeV collected with the ATLAS detector at the Large Hadron Collider. In events in which a W boson decays to an electron or muon, the charm quark is tagged either by its semileptonic decay to a muon or by the presence of a charmed meson. The integrated and differential cross sections as a function of the pseudorapidity of the lepton from the W-boson decay are measured. Results are compared to the predictions of next-to-leading-order QCD calculations obtained from various parton distribution function parameterisations. The ratio of the strange-to-down sea-quark distributions is determined to be 0.96(-0.30)(+0.26) at Q (2) = 1.9 GeV2, which supports the hypothesis of an SU(3)-symmetric composition of the light-quark sea. Additionally, the cross-section ratio sigma(W (+) +)/sigma(W (-) + c) is compared to the predictions obtained using parton distribution function parameterisations with different assumptions about the s-(s) over bar quark asymmetry.
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ATLAS Collaboration(Aad, G. et al), Amos, K. R., Aparisi Pozo, J. A., Bailey, A. J., Cabrera Urban, S., Cantero, J., et al. (2023). Measurement of the properties of Higgs boson production at root s=13 TeV in the H→ γγ channel using 139 fb-1 of pp collision data with the ATLAS experiment. J. High Energy Phys., 07(7), 088–100pp.
Abstract: Measurements of Higgs boson production cross-sections are carried out in the diphoton decay channel using 139 fb(-1) of pp collision data at root s = 13TeV collected by the ATLAS experiment at the LHC. The analysis is based on the definition of 101 distinct signal regions using machine-learning techniques. The inclusive Higgs boson signal strength in the diphoton channel is measured to be 1.04(+0.10) (-0.09). Cross-sections for gluon-gluon fusion, vector-boson fusion, associated production with a W or Z boson, and top associated production processes are reported. An upper limit of 10 times the Standard Model prediction is set for the associated production process of a Higgs boson with a single top quark, which has a unique sensitivity to the sign of the top quark Yukawa coupling. Higgs boson production is further characterized through measurements of Simplified Template Cross-Sections (STXS). In total, cross-sections of 28 STXS regions are measured. The measured STXS cross-sections are compatible with their Standard Model predictions, with a p-value of 93%. The measurements are also used to set constraints on Higgs boson coupling strengths, as well as on new interactions beyond the Standard Model in an effective field theory approach. No significant deviations from the Standard Model predictions are observed in these measurements, which provide significant sensitivity improvements compared to the previous ATLAS results.
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LHCb Collaboration(Aaij, R. et al), Martinez-Vidal, F., Oyanguren, A., Ruiz Valls, P., & Sanchez Mayordomo, C. (2016). Measurement of the properties of the Xi(b)(*0) baryon. J. High Energy Phys., 05(5), 161–19pp.
Abstract: We perform a search for near-threshold I (b) (0) resonances decaying to I (b) (-) pi (+) in a sample of proton-proton collision data corresponding to an integrated luminosity of 3 fb(-1) collected by the LHCb experiment. We observe one resonant state, with the following properties: m(Xi b*0) – m (Xi b-) – m (pi+) = 15.727 +/- 0.068 (stat) +/- 0.023 (syst) MeV/c2, Gamma(Xi b*0) = 0.90 +/- 0.16 (stat) +/- 0.08 (syst) MeV. This confirms the previous observation by the CMS collaboration. The state is consistent with the J (P) = 3/2(+)aEuro integral I (b) (au 0) resonance expected in the quark model. This is the most precise determination of the mass and the first measurement of the natural width of this state. We have also measured the ratio sigma(pp -> Xi b*0 X)B(Xi b*0 -> Xi b-pi+)/sigma(pp -> Xi b- X) = 0.28 +/- 0.03 (stat.) +/- 0.01 (syst).
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LHCb Collaboration(Aaij, R. et al), Jaimes Elles, S. J., Jashal, B. K., Martinez-Vidal, F., Oyanguren, A., Rebollo De Miguel, M., et al. (2023). Measurement of the ratio of branching fractions B(B+c → B0sπ+)/B(B+c → J/ψπ+). J. High Energy Phys., 07(7), 066–19pp.
Abstract: The ratio of branching fractions of B-c(+) -> B-s(0)pi(+) and B-c(+) -> J/psi pi(+) decays is measured with proton-proton collision data of a centre-of-mass energy of 13TeV. The data were collected with the LHCb experiment during 2016-2018, corresponding to an integrated luminosity of 5.4 fb(-1). The B-s(0) mesons are reconstructed via the decays B-s(0) -> J/psi phi and B-s(0) -> D-s(-)pi(+). The ratio of branching fractions is measured to be B(B-c(+) -> B-s(0)pi(+))/B(B-c(+) -> J/psi pi(+)) = 91 +/- 10 +/- 8 +/- 3 where the first uncertainty is statistical, the second is systematic and the third is due to the knowledge of the branching fractions of the intermediate state decays.
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LHCb Collaboration(Aaij, R. et al), Martinez-Vidal, F., Oyanguren, A., Remon Alepuz, C., Ruiz Valls, P., & Sanchez Mayordomo, C. (2016). Measurement of the ratio of branching fractions B(B-c(+) -> J/psi K+)/B(B-c(+) -> J/psi pi(+)). J. High Energy Phys., 09(9), 153–15pp.
Abstract: The ratio of branching fractions R-K/pi = B (B-c(+) -> J/psi K+)/B(B-c(+) -> J/psi pi(+)) is measured with pp collision data collected by the LHCb experiment at centre-of-mass energies of 7TeV and 8TeV, corresponding to an integrated luminosity of 3 fb(-1). It is found to be R-K/pi = 0.079 +/- 0.007 +/- 0.003, where the first uncertainty is statistical and the second is systematic. This measurement is consistent with the previous LHCb result, while the uncertainties are significantly reduced.
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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. (2019). Measurement of the ratio of branching fractions of the decays0(2S) and arrange Lambda. J. High Energy Phys., 03(3), 126–16pp.
Abstract: Using pp collisions corresponding to 3 fb integrated luminosity, recorded by the LHCb experiment at centre- of- mass energies of 7 and 8 TeV, the ratio of branching fractions B (0b ! (2 S) ) =B (0b ! J= ) = 0 : 513 0 : 023 (stat) 0 : 016 (syst) 0 : 011 (B) is determined. The first uncertainty is statistical, the second is systematic and the third is due to the external branching fractions used.
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ATLAS Collaboration(Aaboud, M. et al), Alvarez Piqueras, D., Aparisi Pozo, J. A., Bailey, A. J., Barranco Navarro, L., Cabrera Urban, S., et al. (2019). Measurement of the ratio of cross sections for inclusive isolated-photon production in pp collisions at root s=13 and 8 TeV with the ATLAS detector. J. High Energy Phys., 04(4), 093–47pp.
Abstract: The ratio of the cross sections for inclusive isolated-photon production in pp collisions at centre-of-mass energies of 13 and 8 TeV is measured using the ATLAS detector at the LHC. The integrated luminosities of the 13 TeV and 8 TeV datasets are 3.2 fb(-1) and 20.2 fb(-1), respectively. The ratio is measured as a function of the photon transverse energy in different regions of the photon pseudorapidity. The predictions from next-to-leading-order perturbative QCD calculations are compared with the measured ratio. The experimental systematic uncertainties as well as the uncertainties affecting the predictions are evaluated taking into account the correlations between the two centre-of-mass energies, resulting in a reduction of up to a factor of 2.5 (5) in the experimental (theoretical) systematic uncertainties. The predictions based on several parameterisations of the proton parton distribution functions agree with the data within the reduced experimental and theoretical uncertainties. In addition, this ratio to that of the fiducial cross sections for Z boson production at 13 and 8 TeV using the decay channels Z e(+)e(-) and Z (+-) is made and compared with the theoretical predictions. In this double ratio, a further reduction of the experimental uncertainty is obtained because the uncertainties arising from the luminosity measurement cancel out. The predictions describe the measurements of the double ratio within the theoretical and experimental uncertainties.
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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. (2016). Measurement of the relative width difference of the B-0-(B)over-bar(0) system with the ATLAS detector. J. High Energy Phys., 06(6), 081–39pp.
Abstract: This paper presents the measurement of the relative width difference Delta Gamma(d)/Gamma(d) of the B-0-(B) over bar (0) system using the data collected by the Lambda TLAS experiment at the LHC in pp collisions at root s = 7 TeV and root s= 8 TeV and corresponding to an integrated luminosity of 25.2 fb(-1). The value of Delta Gamma(d)/Gamma(d) is obtained by comparing the decay-time distributions of B-0 -> J/Psi K-S and (B) over bar (0) -> J/Psi K*(0)(892) decays. The result is Delta Gamma(d)/Gamma(d) = (-0.1 +/- 1.1 (stat.) +/- 0.9 (syst.)) x 10(-2). Currently, this is the most precise single measurement of AFd/Fd. It agrees with the Standard Model prediction and the measurements by other experiments.
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LHCb Collaboration(Aaij, R. et al), Garcia Martin, L. M., Henry, L., Jashal, B. K., Martinez-Vidal, F., Oyanguren, A., et al. (2020). Measurement of the shape of the B-s(0) -> D-s*(-) mu(+) nu(mu) differential decay rate. J. High Energy Phys., 12(12), 144–32pp.
Abstract: The shape of the B-s(0) -> D-s*mu(+)nu(mu) differential decay rate is obtained as a function of the hadron recoil parameter using proton-proton collision data at a centreof-mass energy of 13TeV, corresponding to an integrated luminosity of 1.7 fb(-1) collected by the LHCb detector. The B-s(0) -> D-s*(-)mu(+)nu(mu) decay is reconstructed through the decays D-s*(-) up arrow D-s(-) gamma and D-s(-) -> K-K+pi(-). The differential decay rate is fitted with the CapriniLellouch-Neubert (CLN) and Boyd-Grinstein-Lebed (BGL) parametrisations of the form factors, and the relevant quantities for both are extracted.
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