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Albaladejo, M., Bibrzycki, L., Dawid, S. M., Fernandez-Ramirez, C., Gonzalez-Solis, S., Hiller Blin, A. N., et al. (2022). Novel approaches in hadron spectroscopy. Prog. Part. Nucl. Phys., 127, 103981–75pp.
Abstract: The last two decades have witnessed the discovery of a myriad of new and unexpected hadrons. The future holds more surprises for us, thanks to new-generation experiments. Understanding the signals and determining the properties of the states requires a parallel theoretical effort. To make full use of available and forthcoming data, a careful amplitude modeling is required, together with a sound treatment of the statistical uncertainties, and a systematic survey of the model dependencies. We review the contributions made by the Joint Physics Analysis Center to the field of hadron spectroscopy.
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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). Observation of structure in the J/psi-pair mass spectrum. Sci. Bull., 65(23), 1983–1993.
Abstract: Using proton-proton collision data at centre-of-mass energies of root s = 7, 8 and 13 TeV recorded by the LHCb experiment at the Large Hadron Collider, corresponding to an integrated luminosity of 9 fb(-1), the invariant mass spectrum of J/psi pairs is studied. A narrow structure around 6.9 GeV/c(2) matching the line-shape of a resonance and a broad structure just above twice the J/psi mass are observed. The deviation of the data from nonresonant J/psi-pair production is above five standard deviations in the mass region between 6.2 and 7.4 GeV/c(2), covering predicted masses of states composed of four charm quarks. The mass and natural width of the narrow X(6900) structure are measured assuming a Breit-Wigner lineshape.
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LHCb Collaboration(Aaij, R. et al), Henry, L., Jashal, B. K., Martinez-Vidal, F., Oyanguren, A., Remon Alepuz, C., et al. (2021). Evidence of a J/psi Lambda structure and observation of excited Xi(-) states in the Xi(-)(b) -> J/psi Lambda K- decay. Sci. Bull., 66(13), 1278–1287.
Abstract: First evidence of a structure in the J/psi Lambda invariant mass distribution is obtained from an amplitude analysis of Xi(-)(b) -> J/psi Lambda K- decays. The observed structure is consistent with being due to a charmonium pentaquark with strangeness with a significance of 3.1r including systematic uncertainties and lookelsewhere effect. Its mass and width are determined to be 4458.8 +/- 2.9(-1.1)(+4.7) MeV and 17.3 +/- 6.5(-5.7)(+8.0) MeV, respectively, where the quoted uncertainties are statistical and systematic. The structure is also consistent with being due to two resonances. In addition, the narrow excited Xi(-) states, Xi(-)(1690) and Xi(-)(1820)(-), are seen for the first time in a Xi(-)(b) decay, and their masses and widths are measured with improved precision. The analysis is performed using pp collision data corresponding to a total integrated luminosity of 9 fb(-1), collected with the LHCb experiment at centre-of-mass energies of 7, 8 and 13 TeV.
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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). Amplitude analysis of the D+s → π-π+π+ decay. J. High Energy Phys., 07(7), 204–35pp.
Abstract: A Dalitz plot analysis of the D-s(+) -> pi(-)pi(+)pi(+) decay is presented. The analysis is based on proton-proton collision data recorded by the LHCb experiment at a centre-of-mass energy of 8TeV and corresponding to an integrated luminosity of 1.5 fb(-1). The resonant structure of the decay is obtained using a quasi-model-independent partial-wave analysis, in which the pi(+)pi(-) S-wave amplitude is parameterised as a generic complex function determined by a fit to the data. The S-wave component is found to be dominant, followed by the contribution from spin-2 resonances and a small contribution from spin-1 resonances. The latter includes the first observation of the D-s(+) -> omega(782)pi(+) channel in the D-s(+) -> pi(-)pi(+)pi(+) decay. The resonant structures of the D-s(+) -> pi(-)pi(+)pi(+) and D+ -> pi(-)pi(+)pi(+) decays are compared, providing information about the mechanisms for the hadron formation in these decays.
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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 new phenomena in multi-body invariant masses in events with at least one isolated lepton and two jets using √s=13 TeV proton-proton collision data collected by the ATLAS detector. J. High Energy Phys., 07(7), 202–44pp.
Abstract: A search for resonances in events with at least one isolated lepton (e or mu) and two jets is performed using 139 fb(-1) of root s = 13 TeV proton-proton collision data recorded by the ATLAS detector at the LHC. Deviations from a smoothly falling background hypothesis are tested in three- and four-body invariant mass distributions constructed from leptons and jets, including jets identified as originating from bottom quarks. Model-independent limits on generic resonances characterised by cascade decays of particles leading to multiple jets and leptons in the final state are presented. The limits are calculated using Gaussian shapes with different widths for the invariant masses. The multi-body invariant masses are also used to set 95% confidence level upper limits on the cross-section times branching ratios for the production and subsequent decay of resonances predicted by several new physics scenarios.
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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). Central exclusive production of J/psi and (2S) mesons in pp collisions at root s=13 TeV. J. High Energy Phys., 10(10), 167–27pp.
Abstract: Measurements are reported of the central exclusive production of J= and ( 2 S) mesons in pp collisions at a centre- of- mass energy of 13 TeV. Backgrounds are signi fi cantly reduced compared to previous measurements made at lower energies through the use of new forward shower counters. The products of the cross- sections and the branching fractions for the decays to dimuons, where both muons are within the pseudorapidity range 2 : 0 < < 4 : 5, are measured to be The fi rst uncertainties are statistical, the second are systematic, and the third are due to the luminosity determination. The cross- sections are also measured di ff erentially for meson rapidities between 2.0 and 4.5. Good agreement is observed with theoretical predictions. Photoproduction cross- sections are derived and compared to previous experiments, and a deviation from a pure power- law extrapolation of lower energy data is observed.
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LHCb Collaboration(Aaij, R. et al), Jashal, B. K., Martinez-Vidal, F., Oyanguren, A., Remon Alepuz, C., & Ruiz Vidal, J. (2022). Measurement of prompt charged-particle production in pp collisions at root s=13 TeV. J. High Energy Phys., 01(1), 166–39pp.
Abstract: The differential cross-section of prompt inclusive production of long-lived charged particles in proton-proton collisions is measured using a data sample recorded by the LHCb experiment at a centre-of-mass energy of root s = 13 TeV. The data sample, collected with an unbiased trigger, corresponds to an integrated luminosity of 5.4 nb(-1). The differential cross-section is measured as a function of transverse momentum and pseudorapidity in the ranges P-T is an element of [80, 10 000) MeV/c and eta is an element of [2.0, 4.8) and is determined separately for positively and negatively charged particles. The results are compared with predictions from various hadronic-interaction models.
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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), Martinez-Vidal, F., Oyanguren, A., Ruiz Valls, P., & Sanchez Mayordomo, C. (2014). Study of the kinematic dependences of Lambda(0)(b) production in pp collisions and a measurement of the Lambda(0)(b) -> Lambda(+)(c)pi(-) branching fraction. J. High Energy Phys., 08(8), 143–19pp.
Abstract: The kinematic dependences of the relative production rates, f(Lambda b)(0)/f(d), of Lambda(0)(b) baryons and B-0 mesons are measured using Lambda(0)(b) -> Lambda(+)(c)pi(-) and (B) over bar (0) -> D+pi(-) decays. The measurements use proton-proton collision data, corresponding to an integrated luminosity of 1 fb(-1) at a centre-of-mass energy of 7 TeV, recorded in the forward region with the LHCb experiment. The relative production rates are observed to depend on the transverse momentum, pT, and pseudorapidity, eta, of the beauty hadron, in the studied kinematic region 1.5 < pT < 40 GeV/c and 2 < eta < 5. Using a previous LHCb measurement of f(Lambda b)(0)/f(d) in semileptonic decays, the branching fraction B (Lambda(0)(b) -> Lambda(+)(c)pi(-)) = (4.30 +/- 0.03(-0.11)(+0.12)+/- 0.26 +/- 0.21) x 10(-3) is obtained, where the first uncertainty is statistical, the second is systematic, the third is from the previous LHCb measurement of f(Lambda b)(0)/f(d) and the fourth is due to the (B) over bar (0) -> D+pi(-) branching fraction. This is the most precise measurement of a Lambda(0)(b) branching fraction to date.
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LHCb Collaboration(Aaij, R. et al), Martinez-Vidal, F., Oyanguren, A., Ruiz Valls, P., & Sanchez Mayordomo, C. (2016). Study of psi(2S) production and cold nuclear matter effects in pPb collisions at root s(NN)=5 TeV. J. High Energy Phys., 03(3), 133–21pp.
Abstract: The production of psi(2S) mesons is studied in dimuon final states using proton-lead (pPb) collision data collected by the LHCb detector. The data sample corresponds to an integrated luminosity of 1.6 nb(-1). The nucleon-nucleon centre-of-mass energy of the pPb collisions is root s(NN) = 5 TeV. The measurement is performed using psi(2S) mesons with transverse momentum less than 14 GeV/c and rapidity y in the ranges 1.5 < y < 4.0 and -5.0 < y < -2.5 in the nucleon-nucleon centre-of-mass system. The forward-backward production ratio and the nuclear modi fi cation factor are determined for psi(2S) mesons. Using the production cross-section results of psi(2S) and J/psi mesons from b-hadron decays, the b (b) over bar cross-section in pPb collisions at root s(NN) = 5 TeV is obtained.
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