Bottom Production Cross Section Research Articles

The ratio R = dσL/dσT in heavy-quark pair leptoproduction as a probe of linearly polarized gluons in unpolarized proton

We study the Callan–Gross ratio R=dσL/dσT in heavy-quark pair leptoproduction, lN→l′QQ¯X, as a probe of linearly polarized gluons inside unpolarized proton, where dσT (dσL) is the differential cross section of the γ⁎N→QQ¯X process initiated by a transverse (longitudinal) virtual photon. Note first that the maximal value for the quantity R allowed by the photon-gluon fusion with unpolarized gluons is large, about 2. We calculate the contribution of the transverse-momentum dependent gluonic counterpart of the Boer–Mulders function, h1⊥g, describing the linear polarization of gluons inside unpolarized proton. Our analysis shows that the maximum value of the ratio R depends strongly on the gluon polarization; it varies from 0 to Q24m2 depending on h1⊥g. We conclude that the Callan–Gross ratio in heavy-quark pair leptoproduction is predicted to be large and very sensitive to the contribution of linearly polarized gluons. For this reason, future measurements of the longitudinal and transverse components of the charm and bottom production cross sections at the proposed EIC and LHeC colliders seem to be very promising for determination of the linear polarization of gluons inside unpolarized proton.

Bottom production from fixed-target to LHC energies

We present a state-of-the-art compilation of the existing bottom production cross sections in elementary collisions, from fixed-target to collider experiments. We then discuss the theoretical uncertainties on the total and differential bottom cross sections in the FONLL approach. In particular, we show total cross sections and kinematical distributions of the bottom hadrons and their decays: B → e / μ X , B → D → e / μ , and B → J / ψ X . After seeing that the calculations give a good description of the existing measurements, we present detailed predictions for the LHC experiments in their specific phase space windows.

Measurement of Bottom Versus Charm as a Function of Transverse Momentum with Electron-Hadron Correlations inp+pCollisions ats=200 GeV

The momentum distribution of electrons from semileptonic decays of charm and bottom quarks for midrapidity |y|<0.35 in p+p collisions at square root of s=200 GeV is measured by the PHENIX experiment at the Relativistic Heavy Ion Collider over the transverse momentum range 2<pT<7 GeV/c. The ratio of the yield of electrons from bottom to that from charm is presented. The ratio is determined using partial D/D-->e(+/-)K(-/+)X (K unidentified) reconstruction. It is found that the yield of electrons from bottom becomes significant above 4 GeV/c in pT. A fixed-order-plus-next-to-leading-log perturbative quantum chromodynamics calculation agrees with the data within the theoretical and experimental uncertainties. The extracted total bottom production cross section at this energy is sigma(bb)=3.2(-1.1)(+1.2)(stat)(-1.3)(+1.4)(syst)mub.

Latest Results on Bottom Spectroscopy and Production with CDF

Using data collected with the CDF Run II detector, new measurements on bottom production cross-sections are presented. The latest achievements in bottom hadron spectroscopy are discussed. The results are based on a large sample of semileptonic and hadronic decays of bottom states made available by triggers based on the precise CDF tracking system.

Bottom production cross section from double muonic decays of b-flavoured hadrons in 920 GeV proton-nucleus collisions

The bb¯ production cross section in 920 GeV proton-nucleus fixed target collisions is measured by observing double muonic decays of b-flavoured hadrons in the kinematic region −0.3<xF(μ)<0.15. A total number of 83±12bb¯ events is obtained with a likelihood fit of the signal and background simulated events to the data. The resulting cross section is σbb¯=17.5±2.6stat±3.3sys nb/nucleon, or, when combined with a previous HERA-B measurement of similar precision, σbb¯=15.8±1.7stat±1.3sysuncorr±2.0syscorr nb/nucleon, which is consistent with recent NLO calculations.

Bottom photoproduction measured using decays into muons in dijet events inepcollisions ats=318GeV

The photoproduction of bottom quarks in events with two jets and a muon has been measured with the ZEUS detector at HERA using an integrated luminosity of 110 ${\mathrm{pb}}^{\mathrm{\ensuremath{-}}1}$. The fraction of jets containing b quarks was extracted from the transverse momentum distribution of the muon relative to the closest jet. Differential cross sections for bottom production as a function of the transverse momentum and pseudorapidity of the muon, of the associated jet and of ${x}_{\ensuremath{\gamma}}^{\mathrm{jets}},$ the fraction of the photon's momentum participating in the hard process, are compared with MC models and QCD predictions made at next-to-leading order. The latter give a good description of the data.

Heavy flavor physics at hadron colliders

The search for the top quark has dominated heavy flavor physics at hadron colliders. For Standard model decay of top the present mass limit is m t > 89 GeV(95% C.L.). Bottom production cross sections are quite large at hadron colliders, thus providing enough statistics for extensive studies. Results on cross sections, B 0 − B 0 mixing, exclusive channels and rare B decays will be summarized.

Limits on D 0- [formula omitted]0 mixing and bottom particle production cross section from hadronically produced same-sign dimuon events

The rates for same-sign and opposite-sign dimuon events with missing energy (indicative of final-state neutrinos) have been measured in 278 GeV π −-Fe and 350 GeV proton-Fe collisions. The main source of opposite-sign events is two semi-leptonic decays of hadronically produced charm states. The same-sign events are consistent with background from pion and kaon decays. We obtain a limit of 0.044 (90% CL) on the fraction of D 0 semileptonic decays that result in the wrong-sign muon and conclude that less than 9% (90% CL) of same-sign dimuon events produced in neutrino interactions can be attributed to D 0- D 0 mixing. The data imply δm < 6.5 × 10 −4 eV and δλ λ < 0.55 for the difference in mass and inverse lifetime of the CP eigenstates of the D 0. Limits on diffractive bottom production cross sections in proton and pion collisions are also presented.