We present results on transverse momentum ($p_{\rm T}$) and rapidity ($y$) differential production cross sections, mean transverse momentum and mean transverse momentum square of inclusive J/$\psi$ and $\psi(2S)$ at forward rapidity ($2.5
Differential production cross sections of $J/\psi$ as a function of $p_{\rm T}$.
Differential production cross sections of $J/\psi$ as a function of rapidity.
Differential production cross sections of $\psi(2S)$ as a function of $p_{\rm T}$.
The production of charged pions, kaons and (anti)protons has been measured at mid-rapidity ($-0.5 y 0$) in p-Pb collisions at $\sqrt{s_{\rm NN}}=5.02$ TeV using the ALICE detector at the LHC. Exploiting particle identification capabilities at high transverse momentum ($p_{\rm T}$), the previously published $p_{\rm T}$ spectra have been extended to include measurements up to 20 GeV/$c$ for seven event multiplicity classes. The $p_{\rm T}$ spectra for pp collisions at $\sqrt{s}=7$ TeV, needed to interpolate a pp reference spectrum, have also been extended up to 20 GeV/$c$ to measure the nuclear modification factor ($R_{\rm pPb}$) in non-single diffractive p-Pb collisions. At intermediate transverse momentum ($2 p_{\rm T} 10$\,GeV/$c$) the proton-to-pion ratio increases with multiplicity in p-Pb collisions, a similar effect is not present in the kaon-to-pion ratio. The $p_{\rm T}$ dependent structure of such increase is qualitatively similar to those observed in pp and heavy-ion collisions. At high $p_{\rm T}$ ($>10$ GeV/$c$), the particle ratios are consistent with those reported for pp and Pb-Pb collisions at the LHC energies. At intermediate $p_{\rm T}$ the (anti)proton $R_{\rm pPb}$ shows a Cronin-like enhancement, while pions and kaons show little or no nuclear modification. At high $p_{\rm T}$ the charged pion, kaon and (anti)proton $R_{\rm pPb}$ are consistent with unity within statistical and systematic uncertainties.
pT-differential invariant yield of charged pions in p-Pb collisions with centre-of-mass energy/nucleon=5.02 TeV, measured for different V0A multiplicity classes. The first uncertainty is statistical, the second one is the total systematic uncertainty, while the third one is the uncorrelated systematic uncertainty which is multiplicity dependent.
pT-differential invariant yield of charged pions in p-Pb collisions with centre-of-mass energy/nucleon=5.02 TeV, measured for NSD events. The first uncertainty is statistical, the second one is the total systematic uncertainty, while the third one is the uncorrelated systematic uncertainty which is multiplicity dependent.
pT-differential invariant yield of charged kaons in p-Pb collisions with centre-of-mass energy/nucleon=5.02 TeV, measured for different V0A multiplicity classes. The first uncertainty is statistical, the second one is the total systematic uncertainty, while the third one is the uncorrelated systematic uncertainty which is multiplicity dependent.
The ALICE Collaboration has measured inclusive J/psi production in pp collisions at a center of mass energy sqrt(s)=2.76 TeV at the LHC. The results presented in this Letter refer to the rapidity ranges |y|<0.9 and 2.5
Double differential J/$\psi$ production cross section at $\sqrt{s}=2.76$ TeV. The first uncertainty is statistical, the second one is $p_{\rm T}$-coorelated, the third one is uncorrelated. Polarization-related uncertainties are not included.
The $\sqrt{s}$-dependence of $\langle p_{\rm T}\rangle$ for inclusive J/$\psi$ production (forward rapidity).
the $\sqrt{s}$-dependence of $\langle p_{\rm T}\rangle$ for inclusive J/$\psi$ production (forward rapidity).
A measurement of the virtual-photon asymmetry A_2(x,Q^2) and of the spin-structure function g_2(x,Q^2) of the proton are presented for the kinematic range 0.004 < x < 0.9 and 0.18 GeV^2 < Q^2 < 20 GeV^2. The data were collected by the HERMES experiment at the HERA storage ring at DESY while studying inclusive deep-inelastic scattering of 27.6 GeV longitudinally polarized leptons off a transversely polarized hydrogen gas target. The results are consistent with previous experimental data from CERN and SLAC. For the x-range covered, the measured integral of g_2(x) converges to the null result of the Burkhardt-Cottingham sum rule. The x^2 moment of the twist-3 contribution to g_2(x) is found to be compatible with zero.
The spin-structure function $xg_2(x,Q^2)$ and virtual-photon asymmetry $A_2(x,Q^2)$ of the proton in bins of $(x,Q^2)$, see text for details. Statistical and systematic uncertainties are presented separately.
The spin-structure function $xg_2$ and the virtual-photon asymmetry $A_2$ of the proton after evolving to common $Q^2$ and averaging over in each $x$-bin (see text for details). Statistical and systematic uncertainties are presented separately.
Correlation matrix for $xg_2$ in 9 $x$-bins (as in Table 2).
Results of inclusive measurements of inelastic electron and positron scattering from unpolarized protons and deuterons at the HERMES experiment are presented. The structure functions $F_2^p$ and $F_2^d$ are determined using a parameterization of existing data for the longitudinal-to-transverse virtual-photon absorption cross-section ratio. The HERMES results provide data in the ranges $0.006\leq x\leq 0.9$ and 0.1 GeV$^2\leq Q^2\leq$ 20 GeV$^2$, covering the transition region between the perturbative and the non-perturbative regimes of QCD in a so-far largely unexplored kinematic region. They are in agreement with existing world data in the region of overlap. The measured cross sections are used, in combination with data from other experiments, to perform fits to the photon-nucleon cross section using the functional form of the ALLM model. The deuteron-to-proton cross-section ratio is also determined.
Results on the differential Born cross section $\frac{d^2\sigma^p}{dx\,dQ^2}$ and $F_2^p$. The statistical uncertainty $\delta_{stat.}$ and the systematic uncertainties $\delta_{PID}$ (particle identification), $\delta_{model}$ (model dependence outside the acceptance), $\delta_{mis.}$ (misalignment), and $\delta_{rad.}$ (Bethe-Heitler efficiencies) are given in percent. Corresponding $x$ bin numbers and $Q^2$ bin numbers and the average values $\langle x \rangle$ and $\langle {Q^2} \rangle$ are listed in the first four columns. The overall normalization uncertainty is 7.6 %. The structure function $F_2^p$ is derived using the parameterization $R=R_{1998}$.
Results on the differential Born cross section $\frac{d^2\sigma^d}{dx\,dQ^2}$ and $F_2^d$. The statistical uncertainty $\delta_{stat.}$ and the systematic uncertainties $\delta_{PID}$ (particle identification), $\delta_{model}$ (model dependence outside the acceptance), $\delta_{mis.}$ (misalignment), and $\delta_{rad.}$ (Bethe-Heitler efficiencies), are given in percent. Corresponding $x$ bin numbers and $Q^2$ bin numbers and the average values $\langle x \rangle$ and $\langle{Q^2}\rangle$ are listed in the first four columns. The overall normalization uncertainty is 7.5 %. The structure function $F_2^d$ is derived using the parameterization $R=R_{1998}$.
Results on the inelastic Born cross-section ratio ${\sigma^d}/{\sigma^p}$. The statistical uncertainty $\delta_{stat.}$, the systematic uncertainty $\delta_{rad.}$ due to radiative corrections and $\delta_{model}$ due to the model dependence outside the acceptance are given in percent. The average values of $x$ and $Q^2$ are listed in the first two columns. The overall normalization uncertainty is 1.4$\%$.
A measurement of the beam-spin asymmetry in the azimuthal distribution of pions produced in semi-inclusive deep-inelastic scattering off protons is presented. The measurement was performed using the {HERMES} spectrometer with a hydrogen gas target and the longitudinally polarized 27.6 GeV positron beam of HERA. The sinusoidal amplitude of the dependence of the asymmetry on the angle $\phi$ of the hadron production plane around the virtual photon direction relative to the lepton scattering plane was measured for $\pi^+,\pi^-$ and $\pi^0$ mesons. The dependence of this amplitude on the Bjorken scaling variable and on the pion fractional energy and transverse momentum is presented. The results are compared to theoretical model calculations.
Beam SSA as a function of Z, X, hadronic PT and Q**2.
Beam SSA as a function of Z, X, hadronic PT and Q**2.
Beam SSA as a function of Z, X, hadronic PT and Q**2.
Precise measurements of the spin structure functions of the proton $g_1^p(x,Q^2)$ and deuteron $g_1^d(x,Q^2)$ are presented over the kinematic range $0.0041 \leq x \leq 0.9$ and $0.18 $ GeV$^2$ $\leq Q^2 \leq 20$ GeV$^2$. The data were collected at the HERMES experiment at DESY, in deep-inelastic scattering of 27.6 GeV longitudinally polarized positrons off longitudinally polarized hydrogen and deuterium gas targets internal to the HERA storage ring. The neutron spin structure function $g_1^n$ is extracted by combining proton and deuteron data. The integrals of $g_1^{p,d}$ at $Q^2=5$ GeV$^2$ are evaluated over the measured $x$ range. Neglecting any possible contribution to the $g_1^d$ integral from the region $x \leq 0.021$, a value of $0.330 \pm 0.011\mathrm{(theo.)}\pm0.025\mathrm{(exp.)}\pm 0.028$(evol.) is obtained for the flavor-singlet axial charge $a_0$ in a leading-twist NNLO analysis.
Integrals of G1 for P, DEUT and N targets.. The second DSYS systematic error is due to the uncertainty in the parameterizations (R, F2, A2, Azz, omegaD).. The third DSYS systematic error is due to the uncertainty in evolving to a common Q**2.
Integrals of G1 for the Non-Singlet contributions.. The second DSYS systematic error is due to the uncertainty in the parameterizations (R, F2, A2, Azz, omegaD).. The third DSYS systematic error is due to the uncertainty in evolving to a common Q**2. Axis error includes +- 5.2/5.2 contribution.
Integrals of G1 over different X ranges for P target at various Q*2 values. The second DSYS systematic error is due to the uncertainty in the parameterizations (R, F2, A2, Azz, omegaD).. The third DSYS systematic error is due to the uncertainty in evolving to a common Q**2. Axis error includes +- 5.2/5.2 contribution.
The Gerasimov-Drell-Hearn (GDH) sum rule connects the anomalous contribution to the magnetic moment of the target nucleus with an energy-weighted integral of the difference of the helicity-dependent photoabsorption cross sections. The data collected by HERMES with a deuterium target are presented together with a re-analysis of previous measurements on the proton. This provides a measurement of the generalised GDH integral covering simultaneously the nucleon-resonance and the deep inelastic scattering regions. The contribution of the nucleon-resonance region is seen to decrease rapidly with increasing $Q^2$. The DIS contribution is sizeable over the full measured range, even down to the lowest measured $Q^2$. As expected, at higher $Q^2$ the data are found to be in agreement with previous measurements of the first moment of $g_1$. From data on the deuteron and proton, the GDH integral for the neutron has been derived and the proton--neutron difference evaluated. This difference is found to satisfy the fundamental Bjorken sum rule at $Q^2 = 5$ GeV$^2$.
The value of the GDH integral, as a function of Q**2 , for the deuteron in three W**2 regions, the total ( > 1 GeV**2), the nucleon resonance ( 1 to 4.2 GeV**2) and the DIS (4.2 to 45 GeV**2).
The value of the GDH integral, as a function of Q**2 , for the proton in three W**2 regions, the total ( > 1 GeV**2), the nucleon resonance ( 1 to 4.2 GeV**2) and the DIS (4.2 to 45 GeV**2).
The value of the GDH integral, as a function of Q**2 , for the neutron in three W**2 regions, the total ( > 1 GeV**2), the nucleon resonance ( 1 to 4.2 GeV**2) and the DIS (4.2 to 45 GeV**2).
Measurements of the individual multiplicities of pi+, pi- and pi0 produced in the deep-inelastic scattering of 27.5 GeV positrons on hydrogen are presented. The average charged pion multiplicity is the same as for neutral pions, up to approximately z= 0.7, where z is the fraction of the energy transferred in the scattering process carried by the pion. This result (below z= 0.7) is consistent with isospin invariance. The total energy fraction associated with charged and neutral pions is 0.51 +/- 0.01 (stat.) +/- 0.08 (syst.) and 0.26 +/- 0.01 (stat.) +/- 0.04 (syst.), respectively. For fixed z, the measured multiplicities depend on both the negative squared four momentum transfer Q^2 and the Bjorken variable x. The observed dependence on Q^2 agrees qualitatively with the expected behaviour based on NLO-QCD evolution, while the dependence on x is consistent with that of previous data after corrections have been made for the expected Q^2-dependence.
The measured PI0 multiplicity. Additional 9 PCT systematic error.
The measured multiplicity for charged pions, individually and the average. Additional 7 PCT systematic error.
The charged pion multiplicity as a function of x for four different z regions.
The dependence on Q^2 (the negative square of the 4-momentum of the exchanged virtual photon) of the generalised Gerasimov-Drell-Hearn integral for the proton has been measured in the range 1.2 GeV^2 < Q^2 < 12 GeV^2 by scattering longitudinally polarised positrons on a longitudinally polarised hydrogen gas target. The contributions of the nucleon-resonance and deep-inelastic regions to this integral have been evaluated separately. The latter has been found to dominate for Q^2 > 3 GeV^2, while both contributions are important at low Q^2. The total integral shows no significant deviation from a 1/Q^2 behaviour in the measured Q^2 range, and thus no sign of large effects due to either nucleon-resonance excitations or non-leading twist.
The GDH integral as a function of Q2 in the resonance region (W**2 = 1 to 4.2 GeV**2), the measured region (W**2=4.2 to 45 GeV**2), and the total region (W**2= 1 to 45 GeV**2).
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