We report on the $W$ and $Z/\gamma^*$ differential and total cross sections as well as the $W^+$/$W^-$ and $(W^+ + W^-)$/$(Z/\gamma^*)$ cross-section ratios measured by the STAR experiment at RHIC in $p+p$ collisions at $\sqrt{s} = 500$ GeV and $510$ GeV. The cross sections and their ratios are sensitive to quark and antiquark parton distribution functions. In particular, at leading order, the $W$ cross-section ratio is sensitive to the $\bar{d}/\bar{u}$ ratio. These measurements were taken at high $Q^2 \sim M_W^2,M_Z^2$ and can serve as input into global analyses to provide constraints on the sea quark distributions. The results presented here combine three STAR data sets from 2011, 2012, and 2013, accumulating an integrated luminosity of 350 pb$^{-1}$. We also assess the expected impact that our $W^+/W^-$ cross-section ratios will have on various quark distributions, and find sensitivity to the $\bar{u}-\bar{d}$ and $\bar{d}/\bar{u}$ distributions.
Differential cross sections, $d\sigma^{fid}_{W^+}/d\eta_{e^+}$, binned in $e^+$ pseudorapidity bins, requiring that $-1 < \eta_e < 1.5$ and $25$ GeV $< E^e_{T} < 50$ GeV. The values labeled 'stat.' and 'eff.' represent the statistical uncertainty and the systematic uncertainty estimated from the efficiencies, respectively. The later is dominated by the 5\% uncertainty in the tracking efficiency, which is common to all the measurements. The value 'sys.' includes all remaining systematic uncertainties, with the exception of the luminosity. The 9\% uncertainty associated with the luminosity measurement is labeled as 'lumi'.
Differential cross sections, $d\sigma^{fid}_{W^-}/d\eta_{e^-}$, binned in $e^-$ pseudorapidity bins, requiring that $-1 < \eta_e < 1.5$ and $25$ GeV $< E^e_{T} < 50$ GeV. The values labeled ``stat.' and ``eff.' represent the statistical uncertainty and the systematic uncertainty estimated from the efficiencies, respectively. The later is dominated by the 5\% uncertainty in the tracking efficiency, which is common to all the measurements. The value ``sys.' includes all remaining systematic uncertainties, with the exception of the luminosity. The 9\% uncertainty associated with the luminosity measurement is labeled as 'lumi'.
Differential cross sections, $d\sigma^{fid}_{Z}/dy_Z$, binned in rapidity bins, requiring that $|\eta_e|<1$, $|y_Z| < 1$, $p^e_T > 15$ GeV, and $ 70$ GeV $< M_Z < 110$ GeV. The values labeled 'stat.' and 'eff.' represent the statistical uncertainty and the systematic uncertainty estimated from the efficiencies, respectively. The later is dominated by the 10\% uncertainty in the tracking efficiency, which is common to all the measurements. The value 'sys.' includes all remaining systematic uncertainties, with the exception of the luminosity. The 9\% uncertainty associated with the luminosity measurement is labeled as 'lumi'.
The STAR Collaboration at the Relativistic Heavy Ion Collider reports the first measurement of inclusive jet production in peripheral and central Au+Au collisions at $\sqrt{s_{NN}}$=200 GeV. Jets are reconstructed with the anti-k$_{T}$ algorithm using charged tracks with pseudorapidity $|\eta|<1.0$ and transverse momentum $0.2<p_{T,jet}^{ch}<30$ GeV/$c$, with jet resolution parameter $R$=0.2, 0.3, and 0.4. The large background yield uncorrelated with the jet signal is observed to be dominated by statistical phase space, consistent with a previous coincidence measurement. This background is suppressed by requiring a high-transverse-momentum (high-$p_T$) leading hadron in accepted jet candidates. The bias imposed by this requirement is assessed, and the $p_T$ region in which the bias is small is identified. Inclusive charged-particle jet distributions are reported in peripheral and central Au+Au collisions for $5<p_{T,jet}^{ch}<25$ GeV/$c$ and $5<p_{T,jet}^{ch}<30$ GeV/$c$, respectively. The charged-particle jet inclusive yield is suppressed for central Au+Au collisions, compared to both the peripheral Au+Au yield from this measurement and to the $pp$ yield calculated using the PYTHIA event generator. The magnitude of the suppression is consistent with that of inclusive hadron production at high $p_T$, and that of semi-inclusive recoil jet yield when expressed in terms of energy loss due to medium-induced energy transport. Comparison of inclusive charged-particle jet yields for different values of $R$ exhibits no significant evidence for medium-induced broadening of the transverse jet profile for $R<0.4$ in central Au+Au collisions. The measured distributions are consistent with theoretical model calculations that incorporate jet quenching.
Corrected inclusive charged-particle jet distributions in Au+Au collisions at 200 GeV for R=0.2, 0.3, and 0.4 in central (0-10%) Au+Au collisions for pTlead,min = 5 GeV/c. The first uncertainty is statistical (symmetric), followed by shape uncertainty (asymmetric) and correlated uncertainty (asymmetric).
Corrected inclusive charged-particle jet distributions in Au+Au collisions at 200 GeV for R=0.2, 0.3, and 0.4 in peripheral (60-80%) Au+Au collisions for pTlead,min = 5 GeV/c. The first uncertainty is statistical (symmetric), followed by shape uncertainty (asymmetric) and correlated uncertainty (asymmetric).
Corrected inclusive charged-particle jet distributions in Au+Au collisions at 200 GeV for R=0.2, 0.3, and 0.4 in central (0-10%) Au+Au collisions for pTlead,min = 7 GeV/c. The first uncertainty is statistical (symmetric), followed by shape uncertainty (asymmetric) and correlated uncertainty (asymmetric).
Measurements of prompt $\psi$(2S) meson production cross sections in proton-lead (pPb) and proton-proton (pp) collisions at a nucleon-nucleon center-of-mass energy of $\sqrt{s_{_\mathrm{NN}}}=$ 5.02 TeV are reported. The results are based on pPb and pp data collected by the CMS experiment at the LHC, corresponding to integrated luminosities of 34.6 nb$^{-1}$ and 28.0 pb$^{-1}$, respectively. The nuclear modification factor $R_\mathrm{pPb}$ is measured for prompt $\psi$(2S) in the transverse momentum range 4 $<$ p$_\mathrm{T}$ $<$ 30 GeV$/c$ and the center-of-mass rapidity range $-$2.4 $< y_\mathrm{cm} <$ 1.93. The results on $\psi$(2S) $R_\mathrm{pPb}$ are compared to the corresponding modification factor for prompt J$/\psi$ mesons and are found to be more suppressed than the J$/\psi$ states over the entire kinematic range studied.
Differential cross section (multiplied by the dimuon branching fraction) of prompt $\psi$(2S) mesons in pPb collisions at $\sqrt(s_{\textrm{NN}})=5.02 $ TeV, as a function of $p_{\textrm{T}}$, for four backward $y_{\mathrm{CM}}$ regions. The fully correlated luminosity uncertainty of 3.5% is not inlcuded in the point-by-point uncertainty.
Differential cross section (multiplied by the dimuon branching fraction) of prompt $\psi$(2S) mesons in pPb collisions at $\sqrt(s_{\textrm{NN}})=5.02 $ TeV, as a function of $p_{\textrm{T}}$, for four backward $y_{\mathrm{CM}}$ regions. The fully correlated luminosity uncertainty of 3.5% is not included in the point-by-point uncertainty. NOTE- The cross section unit is nb (nano barn); the y-axes of the figures in the publication show pb (pico barn) by mistake.
Differential cross section (multiplied by the dimuon branching fraction) of prompt $\psi$(2S) mesons in pPb collisions at $\sqrt(s_{\textrm{NN}})=5.02 $ TeV, as a function of $p_{\textrm{T}}$, for three forward $y_{\mathrm{CM}}$ regions. The fully correlated luminosity uncertainty of 3.5% is not inlcuded in the point-by-point uncertainty.
This paper reports the measurement of J/psi meson production in proton-proton (pp) and proton-lead (pPb) collisions at a center-of-mass energy per nucleon pair of 5.02 TeV by the CMS experiment at the LHC. The data samples used in the analysis correspond to integrated luminosities of 28 inverse picobarns and 35 inverse nanobarns for pp and pPb collisions, respectively. Prompt and nonprompt J/psi mesons, the latter produced from the decay of B mesons, are measured in their dimuon decay channels. Differential cross sections are measured in the transverse momentum range of 2 < pt < 30 GeV/c, and center-of-mass rapidity ranges of abs(y[CM]) < 2.4 (pp) and -2.87 < y[CM] < 1.93 (pPb). The nuclear modification factor, R[pPb], is measured as functions of both pt and y[CM]. Small modifications of the J/psi cross sections are observed in pPb relative to pp collisions. The ratio of J/psi production cross sections in p-going and Pb-going directions, R[FB], studied as functions of pt and y[CM], shows a significant decrease for increasing transverse energy deposited at large pseudorapidities. These results, which cover a wide kinematic range, provide new insight on the role of cold nuclear matter effects on prompt and nonprompt J/psi production.
Differential cross section (multiplied by the dimuon branching fraction) of prompt J/$\psi$ mesons in pp collisions at forward $y_{\mathrm{CM}}$.
Differential cross section (multiplied by the dimuon branching fraction) of prompt J/$\psi$ mesons in pp collisions at backward $y_{\mathrm{CM}}$.
Differential cross section (multiplied by the dimuon branching fraction) of prompt J/$\psi$ mesons in pPb collisions at forward $y_{\mathrm{CM}}$.
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