Measurement Of Beauty Production Research Articles

Measurements of beauty-decay electrons in ALICE at the LHC

Heavy quarks are essential probes of the evolution of the Quark-Gluon Plasma (QGP) created in ultra-relativistic heavy-ion collisions. In particular, the dependencies of the medium-induced parton energy loss on the parton mass and colour charge can be investigated via measurements of open heavy-flavour hadrons. To quantify medium effects in AA collisions, one needs to study p-A collisions in order to disentangle possible cold nuclear matter effects. Thanks to the excellent vertex and impact parameter resolution of ITS and electron-identification capability provided by TPC and TOF in the ALICE experimental setup, measurements of beauty production in pp, p-Pb and Pb-Pb collisions could be done via electrons from semi-leptonic decays of beauty hadrons. The recent measurements of beauty-decay electrons in p-Pb collisions at √s NN = 5.02 TeV and in Pb-Pb collisions at √s NN = 2.76 TeV in ALICE are presented.

Non prompt D-meson measurements with ALICE at the LHC

The production of hadrons with open heavy flavour (charm and beauty) in high-energy nucleus-nucleus collisions is a powerful tool to study the properties of the deconfined phase of strongly interacting matter known as the Quark-Gluon Plasma (QGP). The production of charm and beauty quarks occurs in hard partonic scattering processes in the early stage of the collisions. ALICE is the LHC experiment devoted to the study of heavy-ion physics. It is able to reconstruct charmed mesons in exclusive decays (e.g. D0 →K− π + ) and beauty hadrons in semi-inclusive decays (e.g. B→eX, B→J/ψ X) . At LHC energies a significant component of the inclusive D-meson yield originates from the decay of beauty-flavoured hadrons, whose knowledge is essential to determine the production of prompt D mesons coming from charm quarks. A precise determination of the non-prompt fraction combined with the determination of the inclusive D-meson yield would allow a measurement of beauty production. A data-driven method that exploits the different shapes of the distributions of the transverse-plane impact parameter to the primary vertex of prompt and feed-down D mesons in p-Pb collisions is used in ALICE. An alternative approach based on the D-meson decay length for Pb–Pb collisions is under study.

Measurement of beauty production in deep inelastic scattering at HERA using decays into electrons

The production of beauty quarks in ep interactions has been studied with the ZEUS detector at HERA for exchanged four-momentum squared Q^2 > 10 GeV^2, using an integrated luminosity of 363 pb^{-1}. The beauty events were identified using electrons from semileptonic b decays with a transverse momentum 0.9 < p_T^e < 8 GeV and pseudorapidity |eta^e| < 1.5. Cross sections for beauty production were measured and compared with next-to-leading-order QCD calculations. The beauty contribution to the proton structure function F_2 was extracted from the double-differential cross section as a function of Bjorken-x and Q^2.

Measurement of beauty production in DIS and extraction at ZEUS

Beauty production in deep inelastic scattering with events in which a muon and a jet are observed in the final state has been measured with the ZEUS detector at HERA using an integrated luminosity of 114 pb^-1. The fraction of events with beauty quarks in the data was determined using the distribution of the transverse momentum of the muon relative to the jet. The cross section for beauty production was measured in the kinematic range of photon virtuality, Q^2 > 2 Gev^2, and inelasticity, 0.05 < y < 0.7, with the requirement of a muon and a jet. Total and differential cross sections are presented and compared to QCD predictions. The beauty contribution to the structure function F_2 was extracted and is compared to theoretical predictions.

Measurement of beauty production from dimuon events at HERA

Beauty production in events containing two muons in the final state has been measured with the ZEUS detector at HERA using an integrated luminosity of 114 pb(-1). A low transverse-momentum threshold for muon identification, in combination with the large rapidity coverage of the ZEUS muon system, gives access to almost the full phase space for beauty production. The total cross section for beauty production in e p collisions at root s = 318 GeV has been measured to be sigma(tot)(ep -> b (b) over barX) = 13.9 +/- 1.5(stat.)(-4.3)(+4.0)(syst.) nb. Differential cross sections and a measurement of b (b) over bar correlations are also obtained, and compared to other beauty cross-section measurements, Monte Carlo models and next-to-leading-order QCD predictions.

Measurement of beauty production in deep inelastic scattering at HERA

The beauty production cross section for deep inelastic scattering events with at least one hard jet in the Breit frame together with a muon has been measured, for photon virtualities Q 2 > 2 GeV 2 , with the ZEUS detector at HERA using integrated luminosity of 72 pb −1 . The total visible cross section is σ b b ¯ ( e p → e jet μ X ) = 40.9 ± 5.7 ( stat . ) − 4.4 + 6.0 ( syst . ) pb . The next-to-leading order QCD prediction lies about 2.5 standard deviations below the data. The differential cross sections are in general consistent with the NLO QCD predictions; however at low values of Q 2 , Bjorken x , and muon transverse momentum, and high values of jet transverse energy and muon pseudorapidity, the prediction is about two standard deviations below the data.

Measurement of beauty production in deep inelastic scattering at HERA

The beauty production cross section for deep inelastic scattering events with at least one hard jet in the Breit frame together with a muon has been measured, for photon virtualities Q2>2 GeV2, with the ZEUS detector at HERA using integrated luminosity of 72 pb−1. The total visible cross section is σbb¯(ep→e jet μX)=40.9±5.7(stat.)−4.4+6.0(syst.) pb. The next-to-leading order QCD prediction lies about 2.5 standard deviations below the data. The differential cross sections are in general consistent with the NLO QCD predictions; however at low values of Q2, Bjorken x, and muon transverse momentum, and high values of jet transverse energy and muon pseudorapidity, the prediction is about two standard deviations below the data.