The photoproduction of $D^{*\pm}$ mesons has been measured with the ZEUS detector at HERA at three different ep centre-of-mass energies, $\sqrt{s}$, of 318, 251 and 225 GeV. For each data set, $D^*$ mesons were required to have transverse momentum, $p_T^{D^*}$, and pseudorapidity, $\eta^{D^*}$, in the ranges $1.9 < p_T^{D^*} < 20$ GeV and $|\eta^{D^*}|<1.6$. The events were required to have a virtuality of the incoming photon, $Q^2$, of less than 1 GeV$^2$. The dependence on $\sqrt{s}$ was studied by normalising to the high-statistics measurement at $\sqrt{s} =318$ GeV. This led to the cancellation of a number of systematic effects both in data and theory. Predictions from next-to-leading-order QCD describe the $\sqrt{s}$ dependence of the data well.
The cross sections for the production of D*+- mesons normalised to the HER data sample.
The reduced cross sections for $e^{+}p$ deep inelastic scattering have been measured with the ZEUS detector at HERA at three different centre-of-mass energies, $318$, $251$ and $225$ GeV. The cross sections, measured double differentially in Bjorken $x$ and the virtuality, $Q^2$, were obtained in the region $0.13\ \leq\ y\ \leq\ 0.75$, where $y$ denotes the inelasticity and $5\ \leq\ Q^2\ \leq\ 110$ GeV$^2$. The proton structure functions $F_2$ and $F_L$ were extracted from the measured cross sections.
The reduced cross section for the reaction E+ P --> E+ X at a centre-of-mass energy 318 GeV and Q^2=7 GeV^2 for the central-vertex region. The (sys) error shown in the table is the total systematic uncertainty, excluding the normalisation uncertainties shown separately below.
The reduced cross section for the reaction E+ P --> E+ X at a centre-of-mass energy 318 GeV and Q^2=9 GeV^2 for the central-vertex region. The (sys) error shown in the table is the total systematic uncertainty, excluding the normalisation uncertainties shown separately below.
The reduced cross section for the reaction E+ P --> E+ X at a centre-of-mass energy 318 GeV and Q^2=12 GeV^2 for the central-vertex region. The (sys) error shown in the table is the total systematic uncertainty, excluding the normalisation uncertainties shown separately below.
The production of beauty and charm quarks in ep interactions has been studied with the ZEUS detector at HERA for exchanged four-momentum squared 5 < Q^2 < 1000 GeV^2 using an integrated luminosity of 354 pb^{-1}. The beauty and charm content in events with at least one jet have been extracted using the invariant mass of charged tracks associated with secondary vertices and the decay-length significance of these vertices. Differential cross sections as a function of Q^2, Bjorken x, jet transverse energy and pseudorapidity were measured and compared with next-to-leading-order QCD calculations. The beauty and charm contributions to the proton structure functions were extracted from the double-differential cross section as a function of x and Q^2. The running beauty-quark mass, m_b at the scale m_b, was determined from a QCD fit at next-to-leading order to HERA data for the first time and found to be 4.07 \pm 0.14 (fit} ^{+0.01}_{-0.07} (mod.) ^{+0.05}_{-0.00} (param.) ^{+0.08}_{-0.05} (theo) GeV.
Differential cross sections for inclusive jet production in beauty events as a function of ET(JET) for ET(JET) > 5 GeV. The measurements are given together with their statistical and systematic uncertainties. Hadronisation and QED radiative corrections, CHAD and CRAD, respectively, are also shown.
Differential cross sections for inclusive jet production in charm events as a function of ET(JET) for ET(JET) > 4.2 GeV. The measurements are given together with their statistical and systematic uncertainties. Hadronisation and QED radiative corrections, CHAD and CRAD, respectively, are also shown.
Differential cross sections for inclusive jet production in beauty events as a function of ETARAP(JET) for -1.6 < ETARAP(JET) < 2.2. The measurements are given together with their statistical and systematic uncertainties. Hadronisation and QED radiative corrections, CHAD and CRAD, respectively, are also shown.
A combination is presented of all inclusive deep inelastic cross sections previously published by the H1 and ZEUS collaborations at HERA for neutral and charged current $e^{\pm}p$ scattering for zero beam polarisation. The data were taken at proton beam energies of 920, 820, 575 and 460 GeV and an electron beam energy of 27.5 GeV. The data correspond to an integrated luminosity of about 1 fb$^{-1}$ and span six orders of magnitude in negative four-momentum-transfer squared, $Q^2$, and Bjorken $x$. The correlations of the systematic uncertainties were evaluated and taken into account for the combination. The combined cross sections were input to QCD analyses at leading order, next-to-leading order and at next-to-next-to-leading order, providing a new set of parton distribution functions, called HERAPDF2.0. In addition to the experimental uncertainties, model and parameterisation uncertainties were assessed for these parton distribution functions. Variants of HERAPDF2.0 with an alternative gluon parameterisation, HERAPDF2.0AG, and using fixed-flavour-number schemes, HERAPDF2.0FF, are presented. The analysis was extended by including HERA data on charm and jet production, resulting in the variant HERAPDF2.0Jets. The inclusion of jet-production cross sections made a simultaneous determination of these parton distributions and the strong coupling constant possible, resulting in $\alpha_s(M_Z)=0.1183 \pm 0.0009 {\rm(exp)} \pm 0.0005{\rm (model/parameterisation)} \pm 0.0012{\rm (hadronisation)} ^{+0.0037}_{-0.0030}{\rm (scale)}$. An extraction of $xF_3^{\gamma Z}$ and results on electroweak unification and scaling violations are also presented.
HERA combined reduced cross sections $\sigma_{r,\rm NC}^{+}$ for NC $e^{+}p$ scattering at $\sqrt{s} = 318$ GeV; $\delta_{\rm stat}$, $\delta_{\rm uncor}$ and $\delta_{\rm cor}$ represent the statistical, uncorrelated systematic and correlated systematic uncertainties, respectively; $\delta_{\rm rel}$, $\delta_{\gamma p}$, $\delta_{\rm had}$ and $\delta_{1}$ to $\delta_{4}$ are the correlated sources of uncertainties arising from the combination procedure. The uncertainties are quoted in percent relative to $\sigma_{r,\rm NC}^{+}$.
HERA combined reduced cross sections $\sigma_{r,\rm NC}^{+}$ for NC $e^{+}p$ scattering at $\sqrt{s} = 300$ GeV; $\delta_{\rm stat}$, $\delta_{\rm uncor}$ and $\delta_{\rm cor}$ represent the statistical, uncorrelated systematic and correlated systematic uncertainties, respectively; $\delta_{\rm rel}$, $\delta_{\gamma p}$, $\delta_{\rm had}$ and $\delta_{1}$ to $\delta_{4}$ are the correlated sources of uncertainties arising from the combination procedure. The uncertainties are quoted in percent relative to $\sigma_{r,\rm NC}^{+}$.
HERA combined reduced cross sections $\sigma_{r,\rm NC}^{+}$ for NC $e^{+}p$ scattering at $\sqrt{s} = 251$ GeV; $\delta_{\rm stat}$, $\delta_{\rm uncor}$ and $\delta_{\rm cor}$ represent the statistical, uncorrelated systematic and correlated systematic uncertainties, respectively; $\delta_{\rm rel}$, $\delta_{\gamma p}$, $\delta_{\rm had}$ and $\delta_{1}$ to $\delta_{4}$ are the correlated sources of uncertainties arising from the combination procedure. The uncertainties are quoted in percent relative to $\sigma_{r,\rm NC}^{+}$.
Photoproduction of beauty quarks in events with two jets and an electron associated with one of the jets has been studied with the ZEUS detector at HERA using an integrated luminosity of 120pb^-1. The fractions of events containing b quarks, and also of events containing c quarks, were extracted from a likelihood fit using variables sensitive to electron identification as well as to semileptonic decays. Total and differential cross sections for beauty and charm production were measured and compared with next-to-leading-order QCD calculations and Monte Carlo models.
Total cross sections for electrons from beauty and charm quarks.
Differential electron cross sections as a function of PT and ETARAP from beauty and charm quarks.
Differential electron cross sections as a function of PT and ETARAP from beauty and charm quarks.
Deep inelastic scattering and its diffractive component, ep -> e'gamma*p ->e'XN, have been studied at HERA with the ZEUS detector using an integrated luminosity of 4.2 pb-1. The measurement covers a wide range in the gamma*p c.m. energy W (37 - 245 GeV), photon virtuality Q2 (2.2 - 80 GeV2) and mass Mx. The diffractive cross section for Mx > 2 GeV rises strongly with W: the rise is steeper with increasing Q2. The latter observation excludes the description of diffractive deep inelastic scattering in terms of the exchange of a single Pomeron. The ratio of diffractive to total cross section is constant as a function of W, in contradiction to the expectation of Regge phenomenology combined with a naive extension of the optical theorem to gamma*p scattering. Above Mx of 8 GeV, the ratio is flat with Q2, indicating a leading-twist behaviour of the diffractive cross section. The data are also presented in terms of the diffractive structure function, F2D(3)(beta,xpom,Q2), of the proton. For fixed beta, the Q2 dependence of xpom F2D(3) changes with xpom in violation of Regge factorisation. For fixed xpom, xpom F2D(3) rises as beta -> 0, the rise accelerating with increasing Q2. These positive scaling violations suggest substantial contributions of perturbative effects in the diffractive DIS cross section.
Measurement of the proton structure function F2 at Q**2 = 2.7 GeV**2.
Measurement of the proton structure function F2 at Q**2 = 4.0 GeV**2.
Measurement of the proton structure function F2 at Q**2 = 6.0 GeV**2.
Isolated photon production in deep inelastic ep scattering has been measured with the ZEUS detector at HERA using an integrated luminosity of 320pb^-1. Measurements were made in the isolated-photon transverse-energy and pseudorapidity ranges 4 < E_T < 15 GeV and -0.7 < eta < 0.9 for exchanged photon virtualities, Q^2, in the range 10 < Q^2 < 350 GeV and for invariant masses of the hadronic system W_X> 5 GeV. Differential cross sections are presented for inclusive isolated photon production as functions of Q^2, x, E_T and eta. Leading-logarithm parton-shower Monte Carlo simulations and perturbative QCD predictions give a reasonable description of the data over most of the kinematic range.
Measured integrated cross section.
Measured differential cross section DSIG/DET.
Measured differential cross section DSIG/DETARAP.
The production of $D^{*\pm}$ mesons in deep inelastic $ep$ scattering has been measured for exchanged photon virtualities $ 5<Q^2<1000 \gev^2 $, using an integrated luminosity of 363 pb$^{-1}$ with the ZEUS detector at HERA. Differential cross sections have been measured and compared to next-to-leading-order QCD calculations. The cross-sections are used to extract the charm contribution to the proton structure functions, expressed in terms of the reduced charm cross section, $\sigma_{\rm red}^{c\bar{c}}$. Theoretical calculations based on fits to inclusive HERA data are compared to the results.
D(SIG)/DPT IN NB/GEV as a function of PT IN GEV.
D(SIG)/DETARAP IN NB as a function of ETARAP.
D(SIG)/DZ IN NB as a function of Z.
This paper presents measurements of \k\ and \lam\ production in neutral current, deep inelastic scattering of 26.7 GeV electrons and 820 GeV protons in the kinematic range $ 10 < Q~{2} < 640 $ GeV$~2$, $0.0003 < x < 0.01$, and $y > 0.04$. Average multiplicities for \k\ and \lam\ production are determined for transverse momenta \ \ptr\ $> 0.5 $ GeV and pseudorapidities $\left| \eta \right| < 1.3$. The multiplicities favour a stronger strange to light quark suppression in the fragmentation chain than found in $e~+ e~-$ experiments. The production properties of \k's in events with and without a large rapidity gap with respect to the proton direction are compared. The ratio of neutral \k's to charged particles per event in the measured kinematic range is, within the present statistics, the same in both samples.
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Production of D*+/-(2010) mesons in diffractive deep inelastic scattering has been measured with the ZEUS detector at HERA using an integrated luminosity of 82 pb^{-1}. Diffractive events were identified by the presence of a large rapidity gap in the final state. Differential cross sections have been measured in the kinematic region 1.5 < Q^2 < 200 GeV^2, 0.02 < y < 0.7, x_{IP} < 0.035, beta < 0.8, p_T(D*+/-) > 1.5 GeV and |\eta(D*+/-)| < 1.5. The measured cross sections are compared to theoretical predictions. The results are presented in terms of the open-charm contribution to the diffractive proton structure function. The data demonstrate a strong sensitivity to the diffractive parton densities.
Total cross section for diffractive D*+- production in the stated kinematicregion.. The second DSYS uncertainty arises from the subtraction of the proton-dissociative background.
The differential cross section as a function of X(NAME=POMERON).
The differential cross section as a function of transverse momentum.
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