Exclusive $\rho^0$ Meson Photoproduction with a Leading Neutron at HERA

The H1 collaboration Andreev, V. ; Baghdasaryan, A. ; Begzsuren, K. ; et al.
Eur.Phys.J.C 76 (2016) 41, 2016.
Inspire Record 1387751 DOI 10.17182/hepdata.74219

A first measurement is presented of exclusive photoproduction of $\rho^0$ mesons associated with leading neutrons at HERA. The data were taken with the H1 detector in the years $2006$ and $2007$ at a centre-of-mass energy of $\sqrt{s}=319$ GeV and correspond to an integrated luminosity of $1.16$ pb$^{-1}$. The $\rho^0$ mesons with transverse momenta $p_T<1$ GeV are reconstructed from their decays to charged pions, while leading neutrons carrying a large fraction of the incoming proton momentum, $x_L>0.35$, are detected in the Forward Neutron Calorimeter. The phase space of the measurement is defined by the photon virtuality $Q^2 < 2$ GeV$^2$, the total energy of the photon-proton system $20 < W_{\gamma p} < 100$ GeV and the polar angle of the leading neutron $\theta_n < 0.75$ mrad. The cross section of the reaction $\gamma p \to \rho^0 n \pi^+$ is measured as a function of several variables. The data are interpreted in terms of a double peripheral process, involving pion exchange at the proton vertex followed by elastic photoproduction of a $\rho^0$ meson on the virtual pion. In the framework of one-pion-exchange dominance the elastic cross section of photon-pion scattering, $\sigma^{\rm el}(\gamma\pi^+ \to \rho^0\pi^+)$, is extracted. The value of this cross section indicates significant absorptive corrections for the exclusive reaction $\gamma p\to\rho^0 n \pi^+$.

11 data tables

The $\gamma p$ cross section integrated in the domain $0.35 < x_L < 0.95$ and $-t^\prime < 1$~GeV$^2$ and averaged over the energy range $20 < W_{\gamma p} < 100$ GeV for two intervals of leading neutron transverse momentum.

Differential photoproduction cross sections ${\rm d}\sigma_{\gamma p}/{\rm d}x_L$ for the exclusive process $\gamma p \to \rho^0 n \pi^+$ in two regions of neutron transverse momentum and $20 < W_{\gamma p} < 100$ GeV. The statistical, uncorrelated and correlated systematic uncertainties, $\delta_{stat}$, $\delta_{sys}^{unc}$ and $\delta_{sys}^{cor}$ respectively, are given, which does not include the global normalisation error of $4.4\%$.

Double differential photoproduction cross sections ${\rm d^2}\sigma_{\gamma p}/{\rm d}x_L{\rm d}p_{T,n}^2$ in the range $20 < W_{\gamma p} < 100$ GeV. The statistical, uncorrelated and correlated systematic uncertainties, $\delta_{stat}$, $\delta_{sys}^{unc}$ and $\delta_{sys}^{cor}$ respectively, are given, which does not include the global normalisation error of $4.4\%$.

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Combination of Differential D^{*\pm} Cross-Section Measurements in Deep-Inelastic ep Scattering at HERA

The H1 & ZEUS collaborations Abramowicz, H. ; Abt, I. ; Adamczyk, L. ; et al.
JHEP 09 (2015) 149, 2015.
Inspire Record 1353667 DOI 10.17182/hepdata.73328

H1 and ZEUS have published single-differential cross sections for inclusive D^{*\pm}-meson production in deep-inelastic ep scattering at HERA from their respective final data sets. These cross sections are combined in the common visible phase-space region of photon virtuality Q2 > 5 GeV2, electron inelasticity 0.02 < y < 0.7 and the D^{*\pm} meson's transverse momentum pT (D^*) > 1.5 GeV and pseudorapidity |eta(D^*)| < 1.5. The combination procedure takes into account all correlations, yielding significantly reduced experimental uncertainties. Double-differential cross sections d2s /dQ2dy are combined with earlier D^{*\pm} data, extending the kinematic range down to Q2 > 1.5 GeV2. Perturbative next-to-leadingorder QCD predictions are compared to the results.

6 data tables

The combined differential $D^{*\pm}$-production cross section as a function of $p_T(D^{*})$, with its uncorrelated and correlated uncertainties.

The combined differential $D^{*\pm}$-production cross section as a function of $\eta(D^{*})$, with its uncorrelated and correlated uncertainties.

The combined differential $D^{*\pm}$-production cross section as a function of $z(D^{*})$, with its uncorrelated and correlated uncertainties.

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Diffractive Dijet Production with a Leading Proton in $ep$ Collisions at HERA

The H1 collaboration Andreev, V. ; Baghdasaryan, A. ; Begzsuren, K. ; et al.
JHEP 05 (2015) 056, 2015.
Inspire Record 1343110 DOI 10.17182/hepdata.73234

The cross section of the diffractive process e^+p -> e^+Xp is measured at a centre-of-mass energy of 318 GeV, where the system X contains at least two jets and the leading final state proton p is detected in the H1 Very Forward Proton Spectrometer. The measurement is performed in photoproduction with photon virtualities Q^2 <2 GeV^2 and in deep-inelastic scattering with 4 GeV^2<Q^2<80 GeV^2. The results are compared to next-to-leading order QCD calculations based on diffractive parton distribution functions as extracted from measurements of inclusive cross sections in diffractive deep-inelastic scattering.

23 data tables

Integrated $e^{+}p$ diffractive dijet cross sections in $\gamma p$. The hadronisation correction factor ($1+\delta_{\text{hadr}}$) applied to the NLO calculation is also listed. The overall normalisation uncertainty of $6\%$ is not included in the table.

Integrated $e^{+}p$ diffractive dijet cross sections in DIS. The hadronisation correction factor ($1+\delta_{\text{hadr}}$) applied to the NLO calculation and the radiative correction ($1+\delta_{\text{rad}}$) are also listed. The overall normalisation uncertainty of $6\%$ is not included in the table.

Ratio of integrated $e^{+}p$ diffractive dijet cross sections for $Q^2<2\,\text{GeV}^2$ (photoproduction) to $Q^2>4\,\text{GeV}^2$ (DIS).

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Measurement of Dijet Production in Diffractive Deep-Inelastic ep Scattering at HERA

The H1 collaboration Andreev, V. ; Baghdasaryan, A. ; Begzsuren, K. ; et al.
JHEP 03 (2015) 092, 2015.
Inspire Record 1332186 DOI 10.17182/hepdata.73124

A measurement is presented of single- and double-differential dijet cross sections in diffractive deep-inelastic $ep$ scattering at HERA using data collected by the H1 experiment corresponding to an integrated luminosity of 290 pb^{-1}. The investigated phase space is spanned by the photon virtuality in the range of 4<Q^{2}<100 GeV^{2} and by the fractional proton longitudinal momentum loss x_pom<0.03. The resulting cross sections are compared with next-to-leading order QCD predictions based on diffractive parton distribution functions and the value of the strong coupling constant is extracted.

11 data tables

Integrated cross section in the measurement phase space.

Diffractive DIS dijet cross section measured differentially as a function of $Q^2$. The global normalisation uncertainty of $7.8\%$ is not listed explicitly but is included in the total systematic uncertainty. The last two columns show the correction factors for hadronisation and QED radiation, respectively.

Diffractive DIS dijet cross section measured differentially as a function of $y$. The global normalisation uncertainty of $7.8\%$ is not listed explicitly but is included in the total systematic uncertainty. The last two column show the correction factors for hadronisation and QED radiation, respectively.

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Diffractive Dijet Photoproduction in ep Collisions at HERA

The H1 collaboration Aaron, F.D. ; Alexa, C. ; Andreev, V. ; et al.
Eur.Phys.J.C 70 (2010) 15-37, 2010.
Inspire Record 857109 DOI 10.17182/hepdata.61487

Measurements are presented of single and double-differential dijet cross sections in diffractive photoproduction based on a data sample with an integrated luminosity of 47 pb^-1. The events are of the type ep -> eXY, where the hadronic system X contains at least two jets and is separated by a large rapidity gap from the system Y, which consists of a leading proton or low-mass proton excitation. The dijet cross sections are compared with QCD calculations at next-to-leading order and with a Monte Carlo model based on leading order matrix elements with parton showers. The measured cross sections are smaller than those obtained from the next-to-leading order calculations by a factor of about 0.6. This suppression factor has no significant dependence on the fraction x_gamma of the photon four-momentum entering the hard subprocess. Ratios of the diffractive to the inclusive dijet cross sections are measured for the first time and are compared with Monte Carlo models.

18 data tables

Total diffractive dijet positron-proton cross section integrated over the full measured kinematic range.

Bin averaged hadron level differential cross section for diffractive dijet production as a function of X(C=GAMMA). The first systematic error is the uncorrelated and the second the correlated uncertainty.

Bin averaged hadron level differential cross section for diffractive dijet production as a function of the ET of jet 1. The first systematic error is the uncorrelated and the second the correlated uncertainty.

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Prompt Photons in Photoproduction at HERA

The H1 collaboration Aaron, F.D. ; Aldaya Martin, M. ; Alexa, C. ; et al.
Eur.Phys.J.C 66 (2010) 17-33, 2010.
Inspire Record 835534 DOI 10.17182/hepdata.56856

The production of prompt photons is measured in the photoproduction regime of electron-proton scattering at HERA. The analysis is based on a data sample corresponding to a total integrated luminosity of 340 pb^-1 collected by the H1 experiment. Cross sections are measured for photons with transverse momentum and pseudorapidity in the range 6 < Et < 15 GeV and -1.0 < eta < 2.4, respectively. Cross sections for events with an additional jet are measured as a function of the transverse energy and pseudorapidity of the jet, and as a function of the fractional momenta x_gamma and x_p carried by the partons entering the hard scattering process. The correlation between the photon and the jet is also studied. The results are compared with QCD predictions based on the collinear and on the k_T factorisation approaches.

17 data tables

Measured inclusive prompt photon cross section in the defined phase space.

Measured prompt photon plus jet cross section in the defined phase space.

Bin averaged differential cross section as a function of ET in the defined phase space.

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Measurement of the D* Meson Production Cross Section and F_2^{ccbar}, at High Q^2, in ep Scattering at HERA

The H1 collaboration Aaron, F.D. ; Alexa, C. ; Alimujiang, K. ; et al.
Phys.Lett.B 686 (2010) 91-100, 2010.
Inspire Record 837434 DOI 10.17182/hepdata.55370

The inclusive production of D*(2010) mesons in deep-inelastic ep scattering is measured in the kinematic region of photon virtuality 100 &lt; Q^2 &lt; 1000 GeV^2 and inelasticity 0.02 &lt; y &lt; 0.7. Single and double differential cross sections for inclusive D* meson production are measured in the visible range defined by |eta(D*)| &lt; 1.5 and p_T(D*) > 1.5 GeV. The data were collected by the H1 experiment during the period from 2004 to 2007 and correspond to an integrated luminosity of 351 pb^{-1}. The charm contribution, F_2^{ccbar}, to the proton structure function F_2 is determined. The measurements are compared with QCD predictions.

12 data tables

Total inclusive cross section for D*+- production.

Single differential cross section DSIG/DPT for D*+- production. The DSYS errors are the uncorrelated and correlated systematicuncertainties respectively.

Single differential cross section DSIG/DETARAP for D*+- production. The DSYS errors are the uncorrelated and correlated systematicuncertainties respectively.

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Strangeness Production at low $Q^2$ in Deep-Inelastic $ep$ Scattering at HERA

The H1 collaboration Aaron, F.D. ; Alexa, C. ; Andreev, V. ; et al.
Eur.Phys.J.C 61 (2009) 185-205, 2009.
Inspire Record 810046 DOI 10.17182/hepdata.45305

The production of neutral strange hadrons is investigated using deep-inelastic scattering events measured with the H1 detector at HERA. The measurements are made in the phase space defined by the negative four-momentum transfer squared of the photon 2 &lt; Q^2 &lt; 100 GeV^2 and the inelasticity 0.1 &lt; y &lt; 0.6. The K_s and Lambda production cross sections and their ratios are determined. K_s production is compared to the production of charged particles in the same region of phase space. The Lambda - anti-Lambda asymmetry is also measured and found to be consistent with zero. Predictions of leading order Monte Carlo programs are compared to the data.

31 data tables

Visible cross section for the production of K0S and LAMBDA(BAR).

Ratio of strange baryon to meson production.

Ratio of K0S to charged hadron production.

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Measurement of isolated photon production in deep-inelastic scattering at HERA

The H1 collaboration Aaron, F.D. ; Aktas, A. ; Alexa, C. ; et al.
Eur.Phys.J.C 54 (2008) 371-387, 2008.
Inspire Record 768933 DOI 10.17182/hepdata.45424

The production of isolated photons in deep-inelastic scattering $ep\to e \gamma X$ is measured with the H1 detector at HERA. The measurement is performed in the kinematic range of negative four-momentum transfer squared $4&lt;Q^2&lt;150 $~GeV$^2$ and a mass of the hadronic system $W_X>50$ GeV. The analysis is based on a total integrated luminosity of 227~pb$^{-1}$. The production cross section of isolatedphotons with a transverse energy in the range $3 &lt; E_T^\gamma &lt; 10$ GeV and pseudorapidity range $-1.2 &lt; \eta^\gamma &lt; 1.8$ is measured as a function of $E_T^\gamma$, $\eta^\gamma$ and $Q^2$. Isolated photon cross sections are also measured for events with no jets or at least one hadronic jet. The measurements are compared with predictions from Monte Carlo generators modelling the photon radiation from the quark and the electron lines, as well as with calculations at leading and next to leading order in the strong coupling. The predictions significantly underestimate the measured cross sections.

15 data tables

Measured inclusive isolated photon cross section.

Measured total cross section for isolated photons plus no-jets and 1-jet.

Differential cross section as a function of the photon ET.

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Three- and Four-jet Production at Low x at HERA

The H1 collaboration Aaron, F.D. ; Aktas, A. ; Alexa, C. ; et al.
Eur.Phys.J.C 54 (2008) 389-409, 2008.
Inspire Record 767896 DOI 10.17182/hepdata.45429

Three- and four-jet production is measured in deep-inelastic $ep$ scattering at low $x$ and $Q^2$ with the H1 detector using an integrated luminosity of $44{.}2 {\rm pb}^{-1}$. Several phase space regions are selected for the three-jet analysis in order to study the underlying parton dynamics from global topologies to the more restrictive regions of forward jets close to the proton direction. The measurements of cross sections for events with at least three jets are compared to fixed order QCD predictions of ${\mathcal{O}}(\alpha_{\rm s}^2)$ and ${\mathcal{O}}(\alpha_{\rm s}^3) $ and with Monte Carlo simulation programs where higher order effects are approximated by parton showers. A good overall description is provided by the ${\mathcal{O}}(\alpha_{\rm s}^3) $ calculation. Too few events are predicted at the lowest $x \sim 10^{-4}$, especially for topologies with two forward jets. This hints to large contributions at low $x$ from initial state radiation of gluons close to the proton direction and unordered in transverse momentum. The Monte Carlo program in which gluon radiation is generated by the colour dipole model gives a good description of both the three- and the four-jet data in absolute normalisation and shape.

23 data tables

Differential cross section as a function of the minimum number of jet for events with at least 3-jets.

Differential cross section as a function of X for events with at least 3-jets.

Differential cross section for events with at least 3-jets as a function of the pseudorapidity of each jet.

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