We have measured the distributions of protons and deuterons produced in high energy heavy ion Au+Au collisions at RHIC over a very wide range of transverse and longitudinal momentum. Near mid-rapidity we have also measured the distribution of anti-protons and anti-deuterons. We present our results in the context of coalescence models. In particular we extract the "volume of homogeneity" and the average phase-space density for protons and anti-protons. Near central rapidity the coalescence parameter $B_2(p_T)$ and the space averaged phase-space density $<f> (p_T)$ are very similar for both protons and anti-protons. For protons we see little variation of either $B_2(p_T)$ or the space averaged phase-space density as the rapidity increases from 0 to 3. However both these quantities depend strongly on $p_T$ at all rapidities. These results are in contrast to lower energy data where the proton and anti-proton phase-space densities are different at $y$=0 and both $B_2$ and $f$ depend strongly on rapidity.
$C_{\Lambda}(p_{\mathrm{T}})$ versus $p_{\mathrm{T}}$ for $\mathrm{\Lambda}$ in $\mathrm{Au}-\mathrm{Au}$ at $\sqrt{s_{\mathrm{NN}}}=200\,\mathrm{Ge\!V}$ near $y=[0, 1, 2, 3]$ for $0-20$% central
$\frac{1}{2\pi p_{\mathrm{T}}}\frac{\mathrm{d}^2N}{\mathrm{d}p_{\mathrm{T}}\mathrm{d}y}$ versus $p_{\mathrm{T}}$ for $\mathrm{p}$ in $\mathrm{Au}-\mathrm{Au}$ at $\sqrt{s_{\mathrm{NN}}}=200\,\mathrm{Ge\!V}$ near $y=0$ for $0-20$% central
$\frac{1}{2\pi p_{\mathrm{T}}}\frac{\mathrm{d}^2N}{\mathrm{d}p_{\mathrm{T}}\mathrm{d}y}$ versus $p_{\mathrm{T}}$ for $\mathrm{d}$ in $\mathrm{Au}-\mathrm{Au}$ at $\sqrt{s_{\mathrm{NN}}}=200\,\mathrm{Ge\!V}$ near $y=0$ for $0-20$% central
Measurements, with the BRAHMS detector, of the antiproton to proton ratio at central and forward rapidities are presented for Au+Au reactions at sqrt{s_{NN}}=130 GeV, and for three different collision centralities. For collisions in the 0-40% centrality range we find $N(\bar{{\rm p}})/N({\rm p}) = 0.64 +- 0.04 (stat.) +- 0.06 (syst.) at y ~0, 0.66 +- 0.03 +- 0.06 at y ~ 0.7, and 0.41 +- 0.04 +- 0.06 at y ~ 2. The ratios are found to be nearly independent of collision centrality and transverse momentum. The measurements demonstrate that the antiproton and proton rapidity densities vary differently with rapidity, and indicate that a net-baryon free midrapidity plateau (Bjorken limit) is not reached at this RHIC energy.
$\overline{\mathrm{p}}/\mathrm{p}$ versus $\mathrm{Centrality}$ for $\overline{\mathrm{p}}$, $\mathrm{p}$ in $\mathrm{Au}-\mathrm{Au}$ at $\sqrt{s_{\mathrm{NN}}}=130\,\mathrm{Ge\!V}$
$\overline{\mathrm{p}}/\mathrm{p}$ versus $p_{\mathrm{T}}$ for $\overline{\mathrm{p}}$, $\mathrm{p}$ in $\mathrm{Au}-\mathrm{Au}$ at $\sqrt{s_{\mathrm{NN}}}=130\,\mathrm{Ge\!V}$
$\overline{\mathrm{p}}/\mathrm{p}$ versus $p_{\mathrm{T}}$ for $\overline{\mathrm{p}}$, $\mathrm{p}$ in $\mathrm{Au}-\mathrm{Au}$ at $\sqrt{s_{\mathrm{NN}}}=130\,\mathrm{Ge\!V}$
We present ratios of the numbers of charged antiparticles to particles (pions, kaons and protons) in Au + Au collisions at $\sqrt{s_{NN}}=200$ GeV as a function of rapidity in the range $y$=0-3. While the particle ratios at midrapidity are approaching unity, the $K^-/K^+$ and $\bar{p}/p$ ratios decrease significantly at forward rapidities. An interpretation of the results within the statistical model indicates a reduction of the baryon chemical potential from $\mu_B \approx 130$MeV at $y$=3 to $\mu_B \approx 25$MeV at $y$=0.
$\mathrm{\pi}^{-}/\mathrm{\pi}^{+}$ versus $p_{\mathrm{T}}$ for $\mathrm{\pi}^{+}$, $\mathrm{\pi}^{-}$ in $\mathrm{Au}-\mathrm{Au}$ at $\sqrt{s_{\mathrm{NN}}}=200\,\mathrm{Ge\!V}$
$\mathrm{K}^{-}/\mathrm{K}^{+}$ versus $p_{\mathrm{T}}$ for $\mathrm{K}^{-}$, $\mathrm{K}^{+}$ in $\mathrm{Au}-\mathrm{Au}$ at $\sqrt{s_{\mathrm{NN}}}=200\,\mathrm{Ge\!V}$
$\overline{\mathrm{p}}/\mathrm{p}$ versus $p_{\mathrm{T}}$ for $\overline{\mathrm{p}}$, $\mathrm{p}$ in $\mathrm{Au}-\mathrm{Au}$ at $\sqrt{s_{\mathrm{NN}}}=200\,\mathrm{Ge\!V}$
Yields for J/psi production in Cu+Cu collisions at sqrt (s_NN)= 200 GeV have been measured by the PHENIX experiment over the rapidity range |y| < 2.2 at transverse momenta from 0 to beyond 5 GeV/c. The invariant yield is obtained as a function of rapidity, transverse momentum and collision centrality, and compared with results in p+p and Au+Au collisions at the same energy. The Cu+Cu data provide greatly improved precision over existing Au+Au data for J/psi production in collisions with small to intermediate numbers of participants, providing a key constraint that is needed for disentangling cold and hot nuclear matter effects.
J/PSI yield versus transverse momentum PT, at mid rapidity : -0.35<y<0.35, for a centrality range of 0-20%.
J/psi-->e+e- invariant yield in Cu+Cu collisions as a function of p_T at mid-rapidity for the 0-20 centrality range. The statistical and systematic uncertainties vary point-to-point and are listed for each measured value. An additional global systematic uncertainty is provided in each column heading, which applies to all data points per column.
J/PSI yield versus transverse momentum PT, at mid rapidity : -0.35<y<0.35, for a centrality range of 20-40%.
This article presents measurements of the $t$-channel single top-quark ($t$) and top-antiquark ($\bar{t}$) total production cross sections $\sigma(tq)$ and $\sigma(\bar{t}q)$, their ratio $R_{t}=\sigma(tq)/\sigma(\bar{t}q)$, and a measurement of the inclusive production cross section $\sigma(tq + \bar{t}q)$ in proton--proton collisions at $\sqrt{s} = 7$ TeV at the LHC. Differential cross sections for the $tq$ and $\bar{t}q$ processes are measured as a function of the transverse momentum and the absolute value of the rapidity of $t$ and $\bar{t}$, respectively. The analyzed data set was recorded with the ATLAS detector and corresponds to an integrated luminosity of 4.59 fb$^{-1}$. Selected events contain one charged lepton, large missing transverse momentum, and two or three jets. The cross sections are measured by performing a binned maximum-likelihood fit to the output distributions of neural networks. The resulting measurements are $\sigma(tq)= 46\pm 6\; \mathrm{pb}$, $\sigma(\bar{t}q)= 23 \pm 4\; \mathrm{pb}$, $R_{t}=2.04\pm 0.18$, and $\sigma(tq + \bar{t}q)= 68 \pm 8\; \mathrm{pb}$, consistent with the Standard Model expectation. The uncertainty on the measured cross sections is dominated by systematic uncertainties, while the uncertainty on $R_{t}$ is mainly statistical. Using the ratio of $\sigma(tq + \bar{t}q)$ to its theoretical prediction, and assuming that the top-quark-related CKM matrix elements obey the relation $|V_{tb}|\gg |V_{ts}|, |V_{td}|$, we determine $|V_{tb}|=1.02 \pm 0.07$.
Differential t-channel top-quark production cross sections and normalized differential t-channel top-quark production cross sections as functions of PT(TOP).
Predicted and observed events yields for the 2-jet and 3-jet channels considered in this measurement. The multijet background is estimated using data-driven techniques (see Sec. VB); an uncertainty of $50\%$ is applied. All the other expectations are derived using theoretical cross sections and their uncertainties (see Secs. VA and VC in the paper).
Differential t-channel top-quark production cross sections and normalized differential t-channel top-quark production cross sections as functions of PT(TOPBAR).
Differential cross sections for the Drell-Yan process, including Z boson production, using the dimuon decay channel are measured in proton-lead (pPb) collisions at a nucleon-nucleon centre-of-mass energy of 8.16 TeV. A data sample recorded with the CMS detector at the LHC is used, corresponding to an integrated luminosity of 173 nb$^{-1}$. The differential cross section as a function of the dimuon mass is measured in the range 15-600 GeV, for the first time in proton-nucleus collisions. It is also reported as a function of dimuon rapidity over the mass ranges 15-60 GeV and 60-120 GeV, and ratios for the p-going over the Pb-going beam directions are built. In both mass ranges, the differential cross sections as functions of the dimuon transverse momentum $p_\mathrm{T}$ and of a geometric variable $\phi^*$ are measured, where $\phi^*$ highly correlates with $p_\mathrm{T}$ but is determined with higher precision. In the Z mass region, the rapidity dependence of the data indicate a modification of the distribution of partons within a lead nucleus as compared to the proton case. The data are more precise than predictions based upon current models of parton distributions.
Differential fiducial cross section (without the acceptance correction) for the DY process measured in the muon channel, as a function of dimuon invariant mass. The quoted error is the quadratic sum of the statistical and systematic uncertainties. The global normalisation uncertainty of 3.5% is listed separately.
Differential fiducial cross section (without the acceptance correction) for the DY process measured in the muon channel, as a function of rapidity in the centre-of-mass frame for $15<m_{\mu\mu}<60$ GeV. The quoted error is the quadratic sum of the statistical and systematic uncertainties. The global normalisation uncertainty of 3.5% is listed separately.
Differential fiducial cross section (without the acceptance correction) for the DY process measured in the muon channel, as a function of rapidity in the centre-of-mass frame for $60<m_{\mu\mu}<120$ GeV. The quoted error is the quadratic sum of the statistical and systematic uncertainties. The global normalisation uncertainty of 3.5% is listed separately.
The BRAHMS collaboration has measured transverse momentum spectra of pions, kaons, protons and antiprotons at rapidities 0 and 3 for Cu+Cu collisions at $\sqrt{s_{NN}} = 200$ GeV. As the collisions become more central the collective radial flow increases while the temperature of kinetic freeze-out decreases. The temperature is lower and the radial flow weaker at forward rapidity. Pion and kaon yields with transverse momenta between 1.5 and 2.5 GeV/c are suppressed for central collisions relative to scaled $p+p$ collisions. This suppression, which increases as the collisions become more central is consistent with jet quenching models and is also present with comparable magnitude at forward rapidity. At such rapidities initial state effects may also be present and persistence of the meson suppression to high rapidity may reflect a combination of jet quenching and nuclear shadowing. The ratio of protons to mesons increases as the collisions become more central and is largest at forward rapidities.
$\frac{1}{2\pi p_{\mathrm{T}}}\frac{\mathrm{d}^2N}{\mathrm{d}p_{\mathrm{T}}\mathrm{d}y}$, $m_{\mathrm{T}}-m_{0}$ versus $p_{\mathrm{T}}$ for $\mathrm{K}^{-}$ in $\mathrm{Cu}-\mathrm{Cu}$ at $\sqrt{s_{\mathrm{NN}}}=200\,\mathrm{Ge\!V}$
$\frac{1}{2\pi p_{\mathrm{T}}}\frac{\mathrm{d}^2N}{\mathrm{d}p_{\mathrm{T}}\mathrm{d}y}$, $m_{\mathrm{T}}-m_{0}$ versus $p_{\mathrm{T}}$ for $\mathrm{K}^{-}$ in $\mathrm{Cu}-\mathrm{Cu}$ at $\sqrt{s_{\mathrm{NN}}}=200\,\mathrm{Ge\!V}$
$\frac{1}{2\pi p_{\mathrm{T}}}\frac{\mathrm{d}^2N}{\mathrm{d}p_{\mathrm{T}}\mathrm{d}y}$, $m_{\mathrm{T}}-m_{0}$ versus $p_{\mathrm{T}}$ for $\mathrm{K}^{-}$ in $\mathrm{Cu}-\mathrm{Cu}$ at $\sqrt{s_{\mathrm{NN}}}=200\,\mathrm{Ge\!V}$
We present spectra of charged pions and protons in 0-10% central Au+Au collisions at $\sqrt{s_{NN}}=200$ GeV at mid-rapidity ($y=0$) and forward pseudorapidity ($\eta=2.2$) measured with the BRAHMS experiment at RHIC. The spectra are compared to spectra from p+p collisions at the same energy scaled by the number of binary collisions. The resulting nuclear modification factors for central Au+Au collisions at both $y=0$ and $\eta=2.2$ exhibit suppression for charged pions but not for (anti-)protons at intermediate $p_T$. The $\bar{p}/\pi^-$ ratios have been measured up to $p_T\sim 3$ GeV/$c$ at the two rapidities and the results indicate that a significant fraction of the charged hadrons produced at intermediate $p_T$ range are (anti-)protons at both mid-rapidity and $\eta = 2.2$.
$\frac{1}{2\pi p_{\mathrm{T}}}\frac{\mathrm{d}^2N}{\mathrm{d}p_{\mathrm{T}}\mathrm{d}y}$ versus $p_{\mathrm{T}}$ for $\overline{\mathrm{p}}$ in $\mathrm{Au}-\mathrm{Au}$ at $\sqrt{s_{\mathrm{NN}}}=200\,\mathrm{Ge\!V}$
$\frac{1}{2\pi p_{\mathrm{T}}}\frac{\mathrm{d}^2N}{\mathrm{d}p_{\mathrm{T}}\mathrm{d}y}$ versus $p_{\mathrm{T}}$ for $\mathrm{\pi}^{-}$ in $\mathrm{Au}-\mathrm{Au}$ at $\sqrt{s_{\mathrm{NN}}}=200\,\mathrm{Ge\!V}$
$\frac{1}{2\pi p_{\mathrm{T}}}\frac{\mathrm{d}^2N}{\mathrm{d}p_{\mathrm{T}}\mathrm{d}y}$ versus $p_{\mathrm{T}}$ for $\mathrm{p}$ in $\mathrm{Au}-\mathrm{Au}$ at $\sqrt{s_{\mathrm{NN}}}=200\,\mathrm{Ge\!V}$
Invariant pT spectra and rapidity densities covering a large rapidity range(-0.1 < y < 3.5) are presented for $\pi^{\pm}$ and $K^{\pm}$ mesons from central Au+Au collisions at $\sqrt{s_{NN}}$ = 62.4 GeV. The mid-rapidity yields of meson particles relative to their anti-particles are found to be close to unity ($\pi^-/\pi^+ \sim 1$, $K^-/K^+ \sim 0.85$) while the anti-proton to proton ratio is $\bar{p}/p \sim 0.49$. The rapidity dependence of the $\pi^-/\pi^+$ ratio is consistent with a small increase towards forward rapidities while the $K^-/K^+$ and $\bar{p}/p$ ratios show a steep decrease to $\sim$ 0.3 for kaons and 0.022 for protons at $y\sim 3$. It is observed that the kaon production relative to its own anti-particle as well as to pion production in wide rapidity and energy ranges shows an apparent universal behavior consistent with the baryo-chemical potential, as deduced from the $\bar{p}/p$ ratio, being the driving parameter.
$\frac{1}{2\pi p_{\mathrm{T}}}\frac{\mathrm{d}^2N}{\mathrm{d}p_{\mathrm{T}}\mathrm{d}y}$ versus $p_{\mathrm{T}}$ for $\mathrm{\pi}^{+}$ in $\mathrm{Au}-\mathrm{Au}$ at $\sqrt{s_{\mathrm{NN}}}=62.4\,\mathrm{Ge\!V}$ near $y=-0.2-0.0$ for $0-10$% central
$\frac{1}{2\pi p_{\mathrm{T}}}\frac{\mathrm{d}^2N}{\mathrm{d}p_{\mathrm{T}}\mathrm{d}y}$ versus $p_{\mathrm{T}}$ for $\mathrm{\pi}^{+}$ in $\mathrm{Au}-\mathrm{Au}$ at $\sqrt{s_{\mathrm{NN}}}=62.4\,\mathrm{Ge\!V}$ near $y=0.0-0.2$ for $0-10$% central
$\frac{1}{2\pi p_{\mathrm{T}}}\frac{\mathrm{d}^2N}{\mathrm{d}p_{\mathrm{T}}\mathrm{d}y}$ versus $p_{\mathrm{T}}$ for $\mathrm{\pi}^{+}$ in $\mathrm{Au}-\mathrm{Au}$ at $\sqrt{s_{\mathrm{NN}}}=62.4\,\mathrm{Ge\!V}$ near $y=0.7-0.9$ for $0-10$% central
We report on a study of the transverse momentum dependence of nuclear modification factors $R_{dAu}$ for charged hadrons produced in deuteron + gold collisions at $\sqrt{s_{NN}=\unit[200]{GeV}$, as a function of collision centrality and of the pseudorapidity ($\eta = 0,1,2.2,3.2 $) of the produced hadrons. We find significant and systematic decrease of $R_{dAu}$ with increasing rapidity. The midrapidity enhancement and the forward rapidity suppression are more pronounced in central collisions relative to peripheral collisions. These results are relevant to the study of the possible onset of gluon saturation at RHIC energies.
$\frac{1}{2\pi p_{\mathrm{T}}}\frac{\mathrm{d}^2N}{\mathrm{d}p_{\mathrm{T}}\mathrm{d}y}$ versus $p_{\mathrm{T}}$ for $\frac{h^{+}+h^{-}}{2}$,$\frac{h^{+}+h^{-}}{2}$ in $\mathrm{p}\mathrm{p}$,$\mathrm{d}-\mathrm{Au}$ at $\sqrt{s}=200\,\mathrm{Ge\!V}$ near $\eta=0$
$\frac{1}{2\pi p_{\mathrm{T}}}\frac{\mathrm{d}^2N}{\mathrm{d}p_{\mathrm{T}}\mathrm{d}y}$ versus $p_{\mathrm{T}}$ for $\frac{h^{+}+h^{-}}{2}$,$\frac{h^{+}+h^{-}}{2}$ in $\mathrm{p}\mathrm{p}$,$\mathrm{d}-\mathrm{Au}$ at $\sqrt{s}=200\,\mathrm{Ge\!V}$ near $\eta=1$
$\frac{1}{2\pi p_{\mathrm{T}}}\frac{\mathrm{d}^2N}{\mathrm{d}p_{\mathrm{T}}\mathrm{d}y}$ versus $p_{\mathrm{T}}$ for $\mathrm{h}^{-}$,$\mathrm{h}^{-}$ in $\mathrm{p}\mathrm{p}$,$\mathrm{d}-\mathrm{Au}$ at $\sqrt{s}=200\,\mathrm{Ge\!V}$ near $\eta=2.2$
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