The Fermilab wide-band antineutrino beam incident on the hydrogen-filled 15-foot bubble chamber was used to study ν¯p neutral-current interactions. The u=x(1−y) distribution is presented for both the neutral- and the charged-current data sample. Fitting the neutral-current u distribution to the prediction of a simple quark-parton model measures the Weinberg angle. By using recent measurements of the neutral-to-charged-current cross-section ratio for νp interactions (Rp), we find the corresponding ratio for ν¯p interactions (R¯p) to be 0.36±0.06.
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We present the results of a study of the inclusive reaction ν¯p→μ+X0 for antineutrino energies from 5 to 150 GeV. The data were obtained by exposing the Fermi National Accelerator Laboratory hydrogen-filled 15-foot bubble chamber to a wide-band antineutrino beam. This is the first high-energy antineutrino experiment in which a pure proton target was used. The experimental problems of selecting the required sample of charged-current antineutrino-induced events are discussed in detail. A Monte Carlo simulation of the experiment is used to provide correction factors to the measured distributions. A measurement of the x dependence of the inelasticity (y) distributions gives the proton structure functions F2ν¯p(x) and xF3ν¯p(x) up to an overall normalization constant. When expressed in terms of the quark-parton model, the quark distributions u(x) and d¯(x)+s¯(x) are determined. The results for u(x) are found to be in excellent agreement with models based on fits to electron and muon scattering data. Using these results to fix the u(x) normalization, an absolute measurement is made of x[d¯(x)+s¯(x)], the antiquark momentum distribution.
VALUES OF Q**2 ASSOCIATED WITH THE FOLLOWING TABLE ARE.... 2.2 , 3.5 , 3.4 , 4.4 , 4.7 , 5.0 , 6.0 , 6.5 , 7.7 , 8.0.
We present the multiplicity distributions of the hadrons produced in antineutrinoproton interactions. The data sample, which consists of 2025 charged-current events with antineutrino energy greater than 5 GeV, comes from exposures of the 15-foot hydrogen bubble chamber to the broad-band antineutrino beam at Fermilab. The distribution in hadronic mass W has an average value of 3.7 GeV but extends up to 10 GeV. The mean multiplicity of charged hadrons depends on the hadronic mass W and varies as 〈nch〉=(−0.44±0.13)+(1.48±0.06)lnW2 for W2>4 GeV2. The mean multiplicities for events with three or more charged tracks averaged over the total data sample are 〈n−〉=1.68±0.03 and 〈n0〉=1.11±0.07 for π− and π0 production, respectively. The mean π0 multiplicity is found to increase slowly with n−. The integrated correlation coefficient f2−− and the dispersion D− are given as a function of n−. When compared to the distributions characteristic of other leptonic and hadronic reactions, we find a similarity between the ν¯ data and results from hadronic reactions that have no diffractive component. Multiplicity data for the heavier particles K0, ρ0, and Λ are also summarized. The pion multiplicities in the current fragmentation region exceed those for the target fragmentation at all W values. They also satisfy the isospin relation 2〈n0〉=〈n+〉+〈n−〉 required for the fragmentation of an I=12 quark when a W>4 GeV selection is imposed.
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The inclusive polarized structure functions of the proton and deuteron, g1p and g1d, were measured with high statistical precision using polarized 6 GeV electrons incident on a polarized ammonia target in Hall B at Jefferson Laboratory. Electrons scattered at lab angles between 18 and 45 degrees were detected using the CEBAF Large Acceptance Spectrometer (CLAS). For the usual DIS kinematics, Q^2>1 GeV^2 and the final-state invariant mass W>2 GeV, the ratio of polarized to unpolarized structure functions g1/F1 is found to be nearly independent of Q^2 at fixed x. Significant resonant structure is apparent at values of W up to 2.3 GeV. In the framework of perturbative QCD, the high-W results can be used to better constrain the polarization of quarks and gluons in the nucleon, as well as high-twist contributions.
Results for G1(P)/F1(P) for the proton in bins of (XB;Q**2), along with average kinematic values and correction factors for each bin. All values are averaged over the event distribution.
Results for G1(DEUT)/F1(DEUT) for the deuteron in bins of (XB;Q**2), along with average kinematic values and correction factors for each bin. All values are averaged over the event distribution.
Results for G1(P)/F1(P) for the proton in bins of (W;Q**2), along with average kinematic values and correction factors for each bin. All values are averaged over the event distribution.
A systematic study is presented for centrality, transverse momentum ($p_T$) and pseudorapidity ($\eta$) dependence of the inclusive charged hadron elliptic flow ($v_2$) at midrapidity($|\eta| < 1.0$) in Au+Au collisions at $\sqrt{s_{NN}}$ = 7.7, 11.5, 19.6, 27 and 39 GeV. The results obtained with different methods, including correlations with the event plane reconstructed in a region separated by a large pseudorapidity gap and 4-particle cumulants ($v_2{4}$), are presented in order to investigate non-flow correlations and $v_2$ fluctuations. We observe that the difference between $v_2{2}$ and $v_2{4}$ is smaller at the lower collision energies. Values of $v_2$, scaled by the initial coordinate space eccentricity, $v_{2}/\varepsilon$, as a function of $p_T$ are larger in more central collisions, suggesting stronger collective flow develops in more central collisions, similar to the results at higher collision energies. These results are compared to measurements at higher energies at the Relativistic Heavy Ion Collider ($\sqrt{s_{NN}}$ = 62.4 and 200 GeV) and at the Large Hadron Collider (Pb + Pb collisions at $\sqrt{s_{NN}}$ = 2.76 TeV). The $v_2(p_T)$ values for fixed $p_T$ rise with increasing collision energy within the $p_T$ range studied ($< 2 {\rm GeV}/c$). A comparison to viscous hydrodynamic simulations is made to potentially help understand the energy dependence of $v_{2}(p_{T})$. We also compare the $v_2$ results to UrQMD and AMPT transport model calculations, and physics implications on the dominance of partonic versus hadronic phases in the system created at Beam Energy Scan (BES) energies are discussed.
The event plane resolutions for Au + Au collisions at $\sqrt{s_{NN}}$ = 7.7, 11.5, 19.6, 27 and 39 GeV as a function of collision centrality.
The comparison of $v_2$ as a function of $p_T$ between GF-cumulant and Q-cumulant methods in Au+Au collisions at $\sqrt{s_{NN}}$ = 39 GeV.
The $p_T$ (> 0.2 GeV/c) and $\eta$ ($∣\eta∣$ < 1) integrated $v_2$ as a function of collision centrality for Au + Au collisions at $\sqrt{s_{NN}}$ = 7.7 GeV, 11.5 GeV, 19.6 GeV, 27 GeV and 39 GeV.
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A search for the quantum chromodynamics (QCD) critical point was performed by the STAR experiment at the Relativistic Heavy Ion Collider, using dynamical fluctuations of unlike particle pairs. Heavy-ion collisions were studied over a large range of collision energies with homogeneous acceptance and excellent particle identification, covering a significant range in the QCD phase diagram where a critical point may be located. Dynamical $K\pi$, $p\pi$, and $Kp$ fluctuations as measured by the STAR experiment in central 0-5\% Au+Au collisions from center-of-mass collision energies $\rm \sqrt{s_{NN}}$ = 7.7 to 200 GeV are presented. The observable $\rm \nu_{dyn}$ was used to quantify the magnitude of the dynamical fluctuations in event-by-event measurements of the $K\pi$, $p\pi$, and $Kp$ pairs. The energy dependences of these fluctuations from central 0-5\% Au+Au collisions all demonstrate a smooth evolution with collision energy.
$p\pi$, Kp, and $K\pi$ fluctuations as a function of collision energy, expressed as $v_{dyn,p\pi}$, $v_{dyn,Kp}$, and $v_{dyn,K\pi}$ respectively. Shown are data from central (0-5%) Au+Au collisions at energies from $\sqrt{s_{\rm NN}}$ = 7.7 to 200 GeV from the STAR experiment.
Results on hyperon production are reported for data accumulated at 10 GeV centre-of-mass energy with the ARGUS detector. Signals for both the octet states Λ, Σ 0 and Ξ − and the decuplet states Σ ± (1385), Ξ 0 (1530) and Ω − are observed 1 (references to a specific state are to be interpreted as also implying the charge conjugate state), some for the first time in e + e − annihilation. Baryon rates from γ dir (1S) decays are enhanced by a factor of about 3 over the continuum.
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We present measurements of the total production rates and momentum distributions of the charmed baryon $\Lambda_c^+$ in $e^+e^- \to$ hadrons at a center-of-mass energy of 10.54 GeV and in $\Upsilon(4S)$ decays. In hadronic events at 10.54 GeV, charmed hadrons are almost exclusively leading particles in $e^+e^- \to c\bar{c}$ events, allowing direct studies of $c$-quark fragmentation. We measure a momentum distribution for $\Lambda_c^+$ baryons that differs significantly from those measured previously for charmed mesons. Comparing with a number of models, we find none that can describe the distribution completely. We measure an average scaled momentum of $\left< x_p \right> = 0.574\pm$0.009 and a total rate of $N_{\Lambda c}^{q\bar{q}} = 0.057\pm$0.002(exp.)$\pm$0.015(BF) $\Lambda_c^+$ per hadronic event, where the experimental error is much smaller than that due to the branching fraction into the reconstructed decay mode, $pK^-\pi^+$. In $\Upsilon (4S)$ decays we measure a total rate of $N_{\Lambda c}^{\Upsilon} = 0.091\pm$0.006(exp.)$\pm$0.024(BF) per $\Upsilon(4S)$ decay, and find a much softer momentum distribution than expected from B decays into a $\Lambda_c^+$ plus an antinucleon and one to three pions.
LAMBDA/C+ differential production rate per hadronic event for the continuum at cm energy 10.54 GeV.
The integrated number of LAMBDA/C+'s per hadronic event for the continuum at cm energy 10.54 GeV.
LAMBDA/C+ differential production rate per UPSILON(4S) decay at cm energy 10.58 GeV.
We have measured theR value in non-resonante+e− annihilation using the ARGUS detector at the storage ring DORIS II. At a centre-of-mass energy\(\sqrt s= 9.36\) GeV the ratio of the hadronic cross-section to the μ-pair cross section in lowest order QED has been determined to beR=3.46±0.03±0.13. In addition, we have measured the charged-particle multiplicities in non-resonant hadron production at\(\sqrt s= 10.47\) GeV just below theB\(\bar B\) threshold and in ϒ (4S) resonance decays. For the average charged-particle multiplicities in continuum events and ϒ(4S)→B\(\bar B\) decays we obtain <n>cont=8.35±0.02±0.20 and <n>ϒ(4s)=10.81±0.05±0.23.
Corrected for radiative effects and acceptance.
Unfolded charged particle multiplicity distribution for continuum events.
Unfolded charged particle multiplicity distribution for UPSILON(4S) events.
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