The interpretation of cosmic antiproton flux measurements from space-borne experiments is currently limited by the knowledge of the antiproton production cross-section in collisions between primary cosmic rays and the interstellar medium. Using collisions of protons with an energy of 6.5 TeV incident on helium nuclei at rest in the proximity of the interaction region of the LHCb experiment, the ratio of antiprotons originating from antihyperon decays to prompt production is measured for antiproton momenta between 12 and 110 GeV/c. The dominant antihyperon contribution, namely $\bar{\Lambda} \to \bar{p} \pi^+$ decays from promptly produced $\bar{\Lambda}$ particles, is also exclusively measured. The results complement the measurement of prompt antiproton production obtained from the same data sample. At the energy scale of this measurement, the antihyperon contributions to antiproton production are observed to be significantly larger than predictions of commonly used hadronic production models.
Ratio of the antihyperon decays to prompt antiproton production (R_Hbar) in collisions of 6.5 TeV protons on He nuclei at rest in antiproton momentum and transverse momentum intervals. The average momentum and transverse momentum, as predicted by the EPOS-LHC generator for prompt antiprotons, are also listed for each interval. The uncertainty is split into an uncorrelated component, denoted with delta_uncorr, and a component that is fully correlated among the kinematic intervals, denoted delta_corr.
Ratio of the Lbar decays to prompt antiproton production (R_Lbar) in collisions of 6.5 TeV protons on He nuclei at rest in antiproton momentum and transverse momentum intervals. The average momentum and transverse momentum, as predicted by the EPOS-LHC generator for prompt antiprotons, are also listed for each interval. The uncertainty is split into an uncorrelated component, denoted with delta_uncorr, and a component that is fully correlated among the kinematic intervals, denoted delta_corr.
Momenta of charged particles produced in inelastic αα, αp, andpp collisions were measured using the Split-Field-Magnet detector at the CERN Intersecting Storage Rings. Inclusive and semi-in-clusive spectra are presented as a function of rapidityy, Feynman-x, and transverse momentumpT. The inclusivey distributions agree well with predictions of the dual parton model; the highest particle densities are reached aty≃0 and the momenta of leading protons decrease significantly for increasing total multiplicity. ‘Temperatures’ are equal in αα, αp, andpp interactions. ThepT distributions depend weakly on the multiplicity.
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Neutron-proton and neutron-deuteron total cross sections have been measured directly at the Princeton-Pennsylvania Accelerator using time of flight to determine the incident neutron momentum. The results cover the region from 700 to 2900 MeVc with a typical accuracy of 0.8% for each of 26 momentum bins. The data are not consistent with the most precise previous measurements in the same momentum range.
No description provided.
We present a new measurement of the inclusive and differential production cross sections of $J/\psi$ mesons and $b$-hadrons in proton-antiproton collisions at $\sqrt{s}=1960$ GeV. The data correspond to an integrated luminosity of 39.7 pb$^{-1}$ collected by the CDF Run II detector. We find the integrated cross section for inclusive $J/\psi$ production for all transverse momenta from 0 to 20 GeV/$c$ in the rapidity range $|y|<0.6$ to be $4.08 \pm 0.02 (stat)^{+0.36}_{-0.33} (syst) \mu {\rm b}$. We separate the fraction of $J/\psi$ events from the decay of the long-lived $b$-hadrons using the lifetime distribution in all events with $p_T(J/\psi) > 1.25$ GeV/$c$. We find the total cross section for $b$-hadrons, including both hadrons and anti-hadrons, decaying to $J/\psi$ with transverse momenta greater than 1.25 GeV/$c$ in the rapidity range $|y(J/\psi)|<0.6$, is $ 0.330 \pm 0.005 (stat) ^{+0.036}_{-0.033} (syst) ~\mu{\rm b}$. Using a Monte Carlo simulation of the decay kinematics of $b$-hadrons to all final states containing a $J/\psi$, we extract the first measurement of the total single $b$-hadron cross section down to zero transverse momentum at $\sqrt{s}=1960$ GeV. We find the total single $b$-hadron cross section integrated over all transverse momenta for $b$-hadrons in the rapidity range $|y|<0.6$ to be $ 17.6 \pm 0.4 (stat)^{+2.5}_{-2.3} (syst) \mu{\rm b}$.
Integrated J/PSI cross section shown both uncorrected and corrected for branching ratio (5.88+-0.10PCT) of J/PSI into mu+mu-. Systematic error includes pT-dependent and fully correlated errors added in quadrature.
Differential cross section times branching ratio (5.88+-0.10PCT) into mu+mu- as a function of transverse momentum for the rapidity range -0.6 to 0.6 at a centre-of-mass energy of 1960 GeV.
Integrated bottom-hadron prouction cross section shown both uncorrected andcorrected for branching ratio (5.88+-0.10PCT) of J/PSI into mu+mu-. Systematic error includes pT-dependent and fully correlated errors added in quadrature.
A search is performed for the production of the ψ(2S) in e+e− annihilation at a center-of-mass energy of 4.03 GeV using the BES detector operated at the Beijing Electron Positron Collider (BEPC). The kinematic features of the reconstructed ψ(2S) signal are consistent with its being produced only in association with an energetic photon resulting from initial state radiation (ISR). Limits are placed on ψ(2S) production from the decay of unknown charmonia or metastable hybrids that might be produced in e+e− annihilations at 4.03 GeV. Under the assumption that the observed cross section for ψ(2S) production is due entirely to ISR, the partial width Γee of the ψ(2S) is measured to be 2.07±0.32keV.
PSI(UNSPEC) is considered as a new 3D2 charmonium state. CHI/C(UNSPEC) is considered as any unknown charmonium state. EXOTIC is considered as a metastable hybrid.
We have measured the B hadron energy distribution in Z0 decays using a sample of semi-leptonic B decays recorded in the SLD experiment at SLAC. The energy of each tagged B hadron was reconstructed using information from the lepton and a partially reconstructed charm-decay vertex. We compared the scaled energy distribution with several models of heavy quark fragmentation. The average scaled energy of primary B hadrons was found to be <x_E_B> = 0.716 +- 0.011 (stat.) +0.022 -0.021 (syst.).
Bin center values for X are given.
No description provided.
We have compared a new QCD calculation by Clay and Ellis of energy-energy correlations (EEC’s) and their asymmetry (AEEC’s) in e+e− annihilation into hadrons with data collected by the SLD experiment at SLAC. From fits of the new calculation, complete at O(αs2), we obtained αs(MZ2)=0.1184±0.0031(expt)±0.0129(theory) (EEC) and αs(MZ2)=0.1120±0.0034(expt)±0.0036(theory) (AEEC). The EEC result is significantly lower than that obtained from comparable fits using the O(αs2) calculation of Kunszt and Nason.
The data are compared to the predictions of Monte-Carlo. Two values of ALPHA_S are corresponded the two theoretical models used in the comparison.
We present a comparison of the strong couplings of light ($u$, $d$, and $s$), $c$, and $b$ quarks determined from multijet rates in flavor-tagged samples of hadronic $Z~0$ decays recorded with the SLC Large Detector at the SLAC Linear Collider. Flavor separation on the basis of lifetime and decay multiplicity differences among hadrons containing light, $c$, and $b$ quarks was made using the SLD precision tracking system. We find: $\alpha_s{_{\vphantom{y}}}~{uds}/{\alpha_s{_{\vphantom{y}}}~{\rm all}} = 0.987 \pm 0.027({\rm stat}) \pm 0.022({\rm syst}) \pm 0.022({\rm theory})$, $\alpha_s{_{\vphantom{y}}}~c/{\alpha_s{_{\vphantom{y}}}~{\rm all}} = 1.012 \pm 0.104 \pm 0.102 \pm 0.096$, and $\alpha_s{_{\vphantom{y}}}~b/{\alpha_s{_{\vphantom{y}}}~{\rm all}} = 1.026 \pm 0.041 \pm 0.041\pm 0.030.$
No description provided.
The dijet invariant mass distribution has been measured in the region between 120 and 1000 GeV/c2, in 1.8-TeV pp¯ collisions. The data sample was collected with the Collider Detector at Fermilab (CDF). Data are compared to leading order (LO) and next-to-leading order (NLO) QCD calculations using two different clustering cone radii R in the jet definition. A quantitative test shows good agreement of data with the LO and NLO QCD predictions for a cone of R=1. The test using a cone of R=0.7 shows less agreement. The NLO calculation shows an improvement compared to LO in reproducing the shape of the spectrum for both radii, and approximately predicts the cone size dependence of the cross section.
Observed cross section using R = 1.0. The second systematic error is the theoretical uncertainty and includes only the effect of the out-of-cone losses, the underlying event energy, and the contribution of multi-jet events.
Observed cross section using R = 0.7. The second systematic error is the theoretical uncertainty and includes only the effect of the out-of-cone losses, the underlying event energy, and the contribution of multi-jet events.
Measurements are reported of the proton and deuteron spin structure functions g1 at beam energies of 29.1, 16.2, and 9.7 GeV and g2 at a beam energy of 29.1 GeV. The integrals of g1 over x have been evaluated at fixed Q**2 = 3 (GeV/c)**2 using the full data set. The Q**2 dependence of the ratio g1/F1 was studied and found to be small for Q**2 > 1 (GeV/c)**2. Within experimental precision the g2 data are well-described by the Wandzura-Wilczek twist-2 contribution. Twist-3 matrix elements were extracted and compared to theoretical predictions. The asymmetry A2 was measured and found to be significantly smaller than the positivity limit for both proton and deuteron targets. A2 for the proton is found to be positive and inconsistent with zero. Measurements of g1 in the resonance region show strong variations with x and Q**2, consistent with resonant amplitudes extracted from unpolarized data. These data allow us to study the Q**2 dependence of the first moments of g1 below the scaling region.
Averaged A1(P) for the DIS (W**2 > 4 GeV) region. Additional normalization uncertainty 3.7%.
Detailed A1(P) for the DIS (W**2 > 4 GeV) region. Additional normalization uncertainty 3.7%.
Detailed A1(P) for the DIS (W**2 > 4 GeV) region. Additional normalization uncertainty 3.7%.
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