A precision measurement of jet cross sections in neutral current deep-inelastic scattering for photon virtualities $5.5<Q^2<80\,{\rm GeV}^2$ and inelasticities $0.2<y<0.6$ is presented, using data taken with the H1 detector at HERA, corresponding to an integrated luminosity of $290\,{\rm pb}^{-1}$. Double-differential inclusive jet, dijet and trijet cross sections are measured simultaneously and are presented as a function of jet transverse momentum observables and as a function of $Q^2$. Jet cross sections normalised to the inclusive neutral current DIS cross section in the respective $Q^2$-interval are also determined. Previous results of inclusive jet cross sections in the range $150<Q^2<15\,000\,{\rm GeV}^2$ are extended to low transverse jet momenta $5<P_{T}^{\rm jet}<7\,{\rm GeV}$. The data are compared to predictions from perturbative QCD in next-to-leading order in the strong coupling, in approximate next-to-next-to-leading order and in full next-to-next-to-leading order. Using also the recently published H1 jet data at high values of $Q^2$, the strong coupling constant $\alpha_s(M_Z)$ is determined in next-to-leading order.
Inclusive jet cross sections measured as a function of $P_T^{\rm jet}$ for $Q^2$ = 5.5-8.0 GeV$^2$. The correction factors on the theoretical cross sections $c^{\rm had}$ are listed together with their uncertainties. The radiative correction factors $c^{\rm rad}$ are already included in the quoted cross sections. Note that the uncertainties labelled $\delta^{E_{e^\prime}}$ and $\delta^{\theta_{e^\prime}}$ in Table 6 of the paper (arXiv:1611.03421v3) should be swapped. See Table 5 of arXiv:1406.4709v2 for details of the correlation model.
Inclusive jet cross sections measured as a function of $P_T^{\rm jet}$ for $Q^2$ = 8.0-11.0 GeV$^2$. The correction factors on the theoretical cross sections $c^{\rm had}$ are listed together with their uncertainties. The radiative correction factors $c^{\rm rad}$ are already included in the quoted cross sections. Note that the uncertainties labelled $\delta^{E_{e^\prime}}$ and $\delta^{\theta_{e^\prime}}$ in Table 6 of the paper (arXiv:1611.03421v3) should be swapped. See Table 5 of arXiv:1406.4709v2 for details of the correlation model.
Inclusive jet cross sections measured as a function of $P_T^{\rm jet}$ for $Q^2$ = 11.0-16.0 GeV$^2$. The correction factors on the theoretical cross sections $c^{\rm had}$ are listed together with their uncertainties. The radiative correction factors $c^{\rm rad}$ are already included in the quoted cross sections. Note that the uncertainties labelled $\delta^{E_{e^\prime}}$ and $\delta^{\theta_{e^\prime}}$ in Table 6 of the paper (arXiv:1611.03421v3) should be swapped. See Table 5 of arXiv:1406.4709v2 for details of the correlation model.
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 series of semi-inclusive deep-inelastic scattering measurements on deuterium, helium, neon, krypton, and xenon targets has been performed in order to study hadronization. The data were collected with the HERMES detector at the DESY laboratory using a 27.6 GeV positron or electron beam. Hadron multiplicities on nucleus A relative to those on the deuteron, R_A^h, are presented for various hadrons (\pi^+, \pi^-, \pi^0, K^+, K^-, p, and \bar{p}) as a function of the virtual-photon energy \nu, the fraction z of this energy transferred to the hadron, the photon virtuality Q^2, and the hadron transverse momentum squared p_t^2. The data reveal a systematic decrease of R_A^h with the mass number A for each hadron type h. Furthermore, R_A^h increases (decreases) with increasing values of \nu (z), increases slightly with increasing Q^2, and is almost independent of p_t^2, except at large values of p_t^2. For pions two-dimensional distributions also are presented. These indicate that the dependences of R_A^{\pi} on \nu and z can largely be described as a dependence on a single variable L_c, which is a combination of \nu and z. The dependence on L_c suggests in which kinematic conditions partonic and hadronic mechanisms may be dominant. The behaviour of R_A^{\pi} at large p_t^2 constitutes tentative evidence for a partonic energy-loss mechanism. The A-dependence of R_A^h is investigated as a function of \nu, z, and of L_c. It approximately follows an A^{\alpha} form with \alpha \approx 0.5 - 0.6.
PI+ multiplicty ratio (Helium/Deuterium) as a function of NU.
K+ multiplicty ratio (Helium/Deuterium) as a function of NU.
P multiplicty ratio (Helium/Deuterium) as a function of NU.
The inclusive e^+ p single and double differential cross sections for neutral and charged current processes are measured with the H1 detector at HERA. The data were taken in 1999 and 2000 at a centre-of-mass energy of \sqrt{s} = 319 GeV and correspond to an integrated luminosity of 65.2 pb^-1. The cross sections are measured in the range of four-momentum transfer squared Q^2 between 100 and 30000 GeV^2 and Bjorken x between 0.0013 and 0.65. The neutral current analysis for the new e^+ p data and the earlier e^- p data taken in 1998 and 1999 is extended to small energies of the scattered electron and therefore to higher values of inelasticity y, allowing a determination of the longitudinal structure function F_L at high Q^2 (110 - 700 GeV^2). A new measurement of the structure function x F_3 is obtained using the new e^+ p and previously published e^\pm p neutral current cross section data at high Q^2. These data together with H1 low Q^2 precision data are further used to perform new next-to-leading order QCD analyses in the framework of the Standard Model to extract flavour separated parton distributions in the proton.
The NC cross section DSIG/DQ**2. There is an additional 1.5 PCT normalization uncertainty.
The CC cross section DSIG/DQ**2. There is an additional 1.5 PCT normalization uncertainty.
The NC cross section DSIG/DX for Q**2 > 1000 GeV**2. There is an additional 1.5 PCT normalization uncertainty.
Inclusive jet cross sections are measured in photoproduction at HERA using the H1 detector. The data sample of e+ p -> e+ + jet + X events in the kinematic range of photon virtualities Q^2 < 1 GeV^2 and photon-proton centre-of-mass energies 95 < W_gammap < 285 GeV represents an integrated luminosity of 24.1 pb^-1. Jets are defined using the inclusive k_T algorithm. Single- and multi-differential cross sections are measured as functions of jet transverse energy E_T^jet and pseudorapidity \eta^jet in the domain 5 < E_T^jet < 75 GeV and -1 < \eta^jet < 2.5. The cross sections are found to be in good agreement with next-to-leading order perturbative QCD calculations corrected for fragmentation and underlying event effects. The cross section differential in E_T^jet, which varies by six orders of magnitude over the measured range, is compared with similar distributions from p pbar colliders at equal and higher energies.
Measured differential E+ P cross section DSIG/DET for inclusive jet photoproduction (Q**2 < 1 GeV**2) integrated over the jet pseudorapidity range -1 to 2.5 in the W(C=GAMMA P) range 95 to 285 GeV.
Measured differential E+ P cross section DSIG/DET for inclusive jet photoproduction (Q**2 < 1 GeV**2) integrated over the jet pseudorapidity range -1 to 2.5 in the W(C=GAMMA P) ranges 95 to 212, and 212 to 285 GeV.
Measured differential E+ P cross section DSIG/DET for inclusive jet photoproduction for the two Q**2 ranges integrated over the jet pseudorapidity range -1to 2.5 in the W(C=GAMMA P) range 164 to 242 GeV.
A measurement of inclusive jet cross-sections in deep-inelastic ep scattering at HERA is presented based on data with an integrated luminosity of 21.1 pb^-1. The measurement is performed for photon virtualities Q^2 between 5 and 100 GeV^2, differentially in Q^2, in the jet transverse energy E_T, in E_T^2/Q^2 and in the pseudorapidity eta_lab. With the renormalization scale mu_R = E_T, perturbative QCD calculations in next-to-leading order (NLO) give a good description of the data in most of the phase space. Significant discrepancies are observed only for jets in the proton beam direction with E_T below 20 GeV and Q^2 below 20 GeV^2. This corresponds to the region in which NLO corrections are largest and further improvement of the calculations is thus of particular interest.
Inclusive jet cross sections DSIG/DET(JET) as a function of ET(JET) in three pseudorapidity ranges.
Inclusive jet cross sections DSIG/DET(JET) as a function of ET(JET) in five Q**2 ranges for the forward pseudorapidity range 1.5 to 2.8.
Inclusive jet cross section DSIG/D(ET**2/Q**2) in the pseudorapidity range -1.0 to 0.5.
An analysis of inelastic photoproduction of J/Psi mesons is presented using data collected at the ep collider HERA corresponding to an integrated luminosity of above 80pb-1. Differential and double differential cross sections are measured in a wide kinematic region: 60<W_gammap<260 GeV, 1<p_t^2< 60 GeV^2 and 0.05<z<0.9, where z is the fraction of the energy of the exchanged photon transferred to the J/Psi meson in the rest frame of the target proton. Cross sections at z<0.3 are presented for the first time. Theoretical calculations within the Colour Singlet Model at NLO for direct photon processes are shown to give a good description of the data in the medium z region (0.3<z<0.9) up to the highest p_t^2 values. A calculation using a k_t factorisation approach in LO in the Colour Singlet Model is also able to describe these data. The data in the full z range are also compared to LO calculations within a non-relativistic QCD framework including color octet and colour singlet contributions for direct and resolved photons. It seems possible to reconcile data and theory with modest contributions from colour octet processes. The polarisation of the J/Psi meson is measured as a function of z and p_t,psi and is reasonably described by the theoretical predictions.
The inelastic J/PSI production cross section as a function of W.
The inelastic J/PSI production cross section as a function of Z.
The double differential cross section for J/PSI production as a function of Z and PT**2.
The leptoproduction of J/psi mesons is studied in inelastic reactions for four momentum transfers 2<Q^2<100GeV^2. The data were taken with the H1 detector at the electron proton collider HERA and correspond to an integrated luminosity of 77 pb-1. Single differential and double differential cross sections are measured with increased precision compared with previous analyses. New leading order calculations within the non-relativistic QCD factorisation approach including colour octet and colour singlet contributions are compared with the data and are found to give a reasonable description of most distributions. An exception is the shape of the distribution in the J/psi fractional energy, z, which deviates significantly from that of the data. Comparisons with photoproduction are made and the polarisation of the produced J/psi meson is analysed.
J/PSI leptoproduction differential cross section as a function of Q**2.
J/PSI leptoproduction differential cross section as a function of Z.
J/PSI leptoproduction differential cross section as a function of W.
The helicity structure of the diffractive electroproduction of rho mesons, e + p -> e + rho + Y, is studied in a previously unexplored region of large four-momentum transfer squared at the proton vertex, t: 0 < t' < 3 GeV^2, where t' = |t| - |t|_min. The data used are collected with the H1 detector at HERA in the kinematic domain 2.5 < Q^2 < 60 GeV^2, 40 < W < 120 GeV. No t dependence of the r^04_00 spin density matrix element is found. A significant t dependent helicity non-conservation from the virtual photon to the rho meson is observed for the spin density matrix element combinations r^5_00+2r^5_11 and r^1_00+2r^1_11. These t dependences are consistently described by a perturbative QCD model based on the exchange of two gluons.
Measurements of the combinations of spin density matrices as a function of TP = |T| - |Tmin|, where |Tmin| is the minimal values of |T| kinematically required for the vector meson and the system X to aquire their effective mass through longitudinal momentum transfer.
Dijet events in photon-proton collisions in which there is a large pseudorapidity separation Delta eta > 2.5 between the two highest E_T jets are studied with the H1 detector at HERA. The inclusive dijet cross sections are measured as functions of the longitudinal momentum fractions of the proton and photon which participate in the production of the jets, x_pjet and x_gjet respectively, Delta eta, the pseudorapidity separation between the two highest E_T jets, and E_T^gap, the total summed transverse energy between the jets. Rapidity gap events are defined as events in which E_T^gap is less than E_T^cut, for E_T^cut varied between 0.5 and 2.0 GeV. The fraction of dijet events with a rapidity gap is measured differentially in Delta eta, x_pjet and x_gjet. An excess of events with rapidity gaps at low values of E_T^cut is observed above the expectation from standard photoproduction processes. This excess can be explained by the exchange of a strongly interacting colour singlet object between the jets.
The inclusive dijet cross section as a function of X(C=GAMMA).
The inclusive dijet cross section as a function of XP.
The inclusive dijet cross section as a function of the rapidity gap.
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