The B 0 s π AE invariant mass distribution is investigated in order to search for possible exotic meson states.The analysis is based on a data sample recorded with the LHCb detector corresponding to 3 fb −1 of pp collision data at ffiffi ffi s p ¼ 7 and 8 TeV. No significant excess is found, and upper limits are set on the production rate of the claimed Xð5568Þ state within the LHCb acceptance. Upper limits are also set as a function of the mass and width of a possible exotic meson decaying to the B 0 s π AE final state. The same limits also apply to a possible exotic meson decaying through the chain B Ã0 s π AE , B Ã0 s → B 0 s γ where the photon is excluded from the reconstructed decays. DOI: 10.1103/PhysRevLett.117.152003 Interest in exotic hadrons has recently intensified, with a wealth of experimental data becoming available [1,2]. All the well-established exotic states contain a heavy quarkantiquark (cc or bb) pair together with additional light particle content. However, the D0 Collaboration has reported evidence [3] of a narrow structure, referred to as the Xð5568Þ, in the B The LHCb detector [6,7] is a single-arm forward spectrometer covering the pseudorapidity range 2 < η < 5, designed for the study of particles containing b or c quarks.
No abstract
A study is presented of central exclusive production of Υ(nS) states, where the Υ(nS) resonances decay to the µ + µ − final state, using pp collision data recorded by the LHCb experiment. The cross-section is measured in the rapidity range 2 < y(Υ) < 4.5 where the muons are reconstructed in the pseudorapidity range 2 < η(µ ± ) < 4.5. The data sample corresponds to an integrated luminosity of 2.9 fb −1 and was collected at centreof-mass energies of 7 TeV and 8 TeV. The measured Υ(1S) and Υ(2S) production crosssections are σ(pp → pΥ(1S)p) = 9.0 ± 2.1 ± 1.7 pb and σ(pp → pΥ(2S)p) = 1.3 ± 0.8 ± 0.3 pb, where the first uncertainties are statistical and the second are systematic. The Υ(1S) crosssection is also measured as a function of rapidity and is found to be in good agreement with Standard Model predictions. An upper limit is set at 3.4 pb at the 95% confidence level for the exclusive Υ(3S) production cross-section, including possible contamination from χ b (3P ) → Υ(3S)γ decays. The LHCb collaboration 15 IntroductionCentral exclusive production (CEP) of Υ(nS) (n = 1, 2, 3) resonances in pp collisions is thought to occur by photoproduction through the exchange of a photon and a pomeron (a colour-singlet system) between two protons, as illustrated in figure 1. Since the protons do not dissociate, typically only a small component of momentum transverse to the beam direction (p T ) is exchanged in the interaction. The photoproduction of Υ resonances at LHCb can be computed using perturbative quantum chromodynamics (QCD), given the high photon-proton centre-of-mass energy, W , and the cross-section depends on the square of the gluon parton-density function, g(x), where Bjorken-x is the fraction of the proton's momentum carried by the gluon [1]. Measurements of the production cross-sections for the Υ(nS) resonances in the forward region covered by the LHCb detector are sensitive to g(x) in the region of small x down to approximately 1.5 × 10 −5 , where the knowledge of g(x) is limited. Furthermore, predictions for the Υ(nS) cross-sections at leading order (LO) and next-to-leading order (NLO) in the strong-interaction coupling differ greatly for the values of W probed in Υ(nS) resonance production, and there are significant variations depending on the models used to describe the Υ wave function and the t-channel exchange [1][2][3]. Quarkonia photoproduction has been studied in exclusive production at HERA [4-9], the Tevatron [10] and the LHC [11][12][13]. At LHCb, exclusive production is associated with the absence of significant detector activity apart from that associated with the exclusive candidate. The background from proton dissociation occurring outside the detector acceptance is characterised as having a value of Υ candidate p T which is larger than that for exclusive production.-1 -
A search for B(s)(0) → μ+ μ- and B0 → μ+ μ decays is performed using 1.0 fb(-1) of pp collision data collected at sqrt[s] = 7 TeV with the LHCb experiment at the Large Hadron Collider. For both decays, the number of observed events is consistent with expectation from background and standard model signal predictions. Upper limits on the branching fractions are determined to be B(B(s)(0) → μ+ μ-) < 4.5(3.8)×10(-9) and B(B0 → μ+ μ-) < 1.0(0.81)×10(-9) at 95% (90%) confidence level.
Determination of γ and −2β s from charmless two-body decays of beauty mesons .LHCb Collaboration a r t i c l e i n f o a b s t r a c tUsing the latest LHCb measurements of time-dependent CP violation in the B 0 s → K + K − decay, a U-spin relation between the decay amplitudes of B 0 s → K + K − and B 0 → π + π − decay processes allows constraints to be placed on the angle γ of the unitarity triangle and on the B 0 s mixing phase −2β s .Results from an extended approach, which uses additional inputs on B 0 → π 0 π 0 and B + → π + π 0 decays from other experiments and exploits isospin symmetry, are also presented. The dependence of the results on the maximum allowed amount of U-spin breaking is studied. At 68% probability, the value γ = (63.5 +7.2 −6.7 ) • modulo 180 • is determined. In an alternative analysis, the value −2β s = −0.12 +0.14 −0.16 rad is found. In both measurements, the uncertainties due to U-spin breaking effects up to 50% are included. decays are related by the U-spin symmetry of strong interactions. This symmetry, related to the exchange of d and s quarks in the decay diagrams, can be exploited to determine the unknown hadronic factors. A more sophisticated analysis has also been proposed [13], where it is suggested to combine the U-spin analysis of B 0 → π + π − and B 0 s → K + K − decays with the isospin analysis of B 0 → π + π − , B 0 → π 0 π 0 and B + → π + π 0 decays [14], in order to achieve a more robust determination of γ with respect to U-spin breaking effects. The B 0, can also be determined with either analysis approach. An analysis based on Bayesian statistics, aimed at determining probability density functions (PDFs) for γ and −2β s , is presented in this Letter. This uses the latest LHCb measurements of time-dependent CP violation in the B 0 s → K + K − decay, exploiting U-spin symmetry with the B 0 → π + π − decay. An extended analysis, including measurements on B 0 → π 0 π 0 and B + → π + π 0 decays from other experiments, is also performed. The Letter is organized as follows. First, the theoretical formalism needed to describe CP violation is introduced in Section 2, including the SM parameterization of the decay amplitudes of the various decays.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.