| 11. |
- Aaron, F. D., et al.
(författare)
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Prompt photons in photoproduction at HERA
- 2010
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Ingår i: European Physical Journal C. Particles and Fields. - : Springer Science and Business Media LLC. - 1434-6044. ; 66:1-2, s. 17-33
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Tidskriftsartikel (refereegranskat)abstract
- 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< E-T(gamma) < 15 GeV and -1.0< eta(gamma) < 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) factorization approaches.
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| 12. |
- Aaron, F. D., et al.
(författare)
-
Diffractive dijet photoproduction in ep collisions at HERA
- 2010
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Ingår i: European Physical Journal C. Particles and Fields. - : Springer Science and Business Media LLC. - 1434-6044. ; 70:1-2, s. 15-37
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 13. |
- Aaron, F. D., et al.
(författare)
-
Inclusive deep inelastic scattering at high Q(2) with longitudinally polarised lepton beams at HERA
- 2012
-
Ingår i: Journal of High Energy Physics. - 1029-8479. ; :9
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Tidskriftsartikel (refereegranskat)abstract
- Inclusive e(+/-)p single and double differential cross sections for neutral and charged current deep inelastic scattering processes are measured with the H1 detector at HERA. The data were taken at a centre-of-mass energy of root s = 319 GeV with a total integrated luminosity of 333.7 pb(-1) shared between two lepton beam charges and two longitudinal lepton polarisation modes. The differential cross sections are measured in the range of negative four-momentum transfer squared, Q(2), between 60 and 50 000GeV(2), and Bjorken x between 0.0008 and 0.65. The measurements are combined with earlier published unpolarised H1 data to improve statistical precision and used to determine the structure function xF(3)(gamma Z). A measurement of the neutral current parity violating structure function F-2(gamma Z) is presented for the first time. The polarisation dependence of the charged current total cross section is also measured. The new measurements are well described by a next-to-leading order QCD fit based on all published H1 inclusive cross section data which are used to extract the parton distribution functions of the proton.
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| 14. |
- Aaron, F. D., et al.
(författare)
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Inclusive measurement of diffractive deep-inelastic scattering at HERA
- 2012
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Ingår i: European Physical Journal C. Particles and Fields. - : Springer Science and Business Media LLC. - 1434-6044. ; 72:7
-
Tidskriftsartikel (refereegranskat)abstract
- The diffractive process ep -> eXY, where Y denotes a proton or its low mass excitation with M-Y < 1.6 GeV, is studied with the H1 experiment at HERA. The analysis is restricted to the phase space region of the photon virtuality 3 <= Q(2) <= 1600 GeV2, the square of the fourmomentum transfer at the proton vertex vertical bar t vertical bar < 1.0 GeV2 and the longitudinal momentum fraction of the incident proton carried by the colourless exchange x(P) < 0.05. Triple differential cross sections are measured as a function of x(P), Q(2) and beta = x/x(P) where x is the Bjorken scaling variable. These measurements are made after selecting diffractive events by demanding a large empty rapidity interval separating the final state hadronic systems X and Y. High statistics measurements covering the data taking periods 1999-2000 and 2004-2007 are combined with previously published results in order to provide a single set of diffractive cross sections from the H1 experiment using the large rapidity gap selection method. The combined data represent a factor between three and thirty increase in statistics with respect to the previously published results. The measurements are compared with predictions from NLO QCD calculations based on diffractive parton densities and from a dipole model. The proton vertex factorisation hypothesis is tested.
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| 15. |
- Aaron, F. D., et al.
(författare)
-
Measurement of the cross section for diffractive deep-inelastic scattering with a leading proton at HERA
- 2011
-
Ingår i: European Physical Journal C. Particles and Fields. - : Springer Science and Business Media LLC. - 1434-6044. ; 71:3
-
Tidskriftsartikel (refereegranskat)abstract
- The cross section for the diffractive deep-inelastic scattering process ep -> eXp is measured, with the leading final state proton detected in the H1 Forward Proton Spectrometer. The data sample covers the range x(P) < 0.1 in fractional proton longitudinal momentum loss, 0.1 < vertical bar t vertical bar < 0.7 GeV2 in squared four-momentum transfer at the proton vertex and 4 < Q(2) < 700 GeV2 in photon virtuality. The cross section is measured four-fold differentially in t, x(P), Q2 and beta = x/x(P), where x is the Bjorken scaling variable. The t and x(P) dependences are interpreted in terms of an effective pomeron trajectory and a sub-leading exchange. The data are compared with perturbative QCD predictions at next-to-leading order based on diffractive parton distribution functions previously extracted from complementary measurements of inclusive diffractive deep-inelastic scattering. The ratio of the diffractive to the inclusive ep cross section is studied as a function of Q(2), beta and x(P).
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| 16. |
- Aaron, F. D., et al.
(författare)
-
Measurement of the inclusive e(+/-) p scattering cross section at high inelasticity y and of the structure function F-L
- 2011
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Ingår i: European Physical Journal C. Particles and Fields. - : Springer Science and Business Media LLC. - 1434-6044. ; 71:3
-
Tidskriftsartikel (refereegranskat)abstract
- A measurement is presented of the inclusive neutral current e(+/-) p scattering cross section using data collected by the H1 experiment at HERA during the years 2003 to 2007 with proton beam energies E-p of 920, 575, and 460 GeV. The kinematic range of the measurement covers low absolute four-momentum transfers squared, 1.5 GeV2 < Q(2) < 120 GeV2, small values of Bjorken x, 2.9 . 10(-5) < x < 0.01, and extends to high inelasticity up to y = 0.85. The structure function F-L is measured by combining the new results with previously published H1 data at E-p = 920 GeV and E-p = 820 GeV. The new measurements are used to test several phenomenological and QCD models applicable in this low Q(2) and low x kinematic domain.
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| 17. |
- Aaron, F. D., et al.
(författare)
-
Search for squarks in R-parity violating supersymmetry in ep collisions at HERA
- 2011
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Ingår i: European Physical Journal C. Particles and Fields. - : Springer Science and Business Media LLC. - 1434-6044. ; 71:3
-
Tidskriftsartikel (refereegranskat)abstract
- A search for squarks in R-parity violating super-symmetry is performed in e(+/-)p collisions at HERA using the H1 detector. The full data sample taken at a centre-of-mass energy root s = 319 GeV is used for the analysis, corresponding to an integrated luminosity of 255 pb(-1) of e(+)p and 183 pb(-1) of e(-)p collision data. The resonant production of squarks via a Yukawa coupling. lambda' is considered, taking into account direct and indirect R-parity violating decay modes. Final states with jets and leptons are investigated. No evidence for squark production is found and mass dependent limits on lambda' are obtained in the framework of the Minimal Supersymmetric Standard Model and in the Minimal Super-gravity Model. In the considered part of the parameter space, for a Yukawa coupling of electromagnetic strength lambda' = 0.3, squarks of all flavours are excluded up to masses of 275 GeV at 95% confidence level, with down-type squarks further excluded up to masses of 290 GeV.
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| 18. |
- Aaron, F. D., et al.
(författare)
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Determination of the integrated luminosity at HERA using elastic QED Compton events
- 2012
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Ingår i: European Physical Journal C. Particles and Fields. - : Springer Science and Business Media LLC. - 1434-6044. ; 72:10
-
Tidskriftsartikel (refereegranskat)abstract
- A measurement of the integrated luminosity at the ep collider HERA is presented, exploiting the elastic QED Compton process ep -> e gamma p. The electron and the photon are detected in the backward calorimeter of the H1 experiment. The integrated luminosity of the data recorded in 2003 to 2007 is determined with a precision of 2.3%. The measurement is found to be compatible with the corresponding result obtained using the Bethe-Heitler process.
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| 19. |
- Aaron, F. D., et al.
(författare)
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Measurement of beauty photoproduction near threshold using di-electron events with the H1 detector at HERA
- 2012
-
Ingår i: European Physical Journal C. Particles and Fields. - : Springer Science and Business Media LLC. - 1434-6044. ; 72:10
-
Tidskriftsartikel (refereegranskat)abstract
- The cross section for ep -> eb (b) over barX in photoproduction is measured with the H1 detector at the ep-collider HERA. The decay channel b (b) over bar -> eeX' is selected by identifying the semi-electronic decays of the b-quarks. The total production cross section is measured in the kinematic range given by the photon virtuality Q(2) <= 1 GeV2, the inelasticity 0.05 <= y <= 0.65 and the pseudorapidity of the b-quarks vertical bar eta(b)vertical bar, vertical bar eta((b) over bar)vertical bar <= 2. The differential production cross section is measured as a function of the average transverse momentum of the beauty quarks < P-T(b)> down to the threshold. The results are compared to next-to-leading-order QCD predictions.
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| 20. |
- Aaron, F. D., et al.
(författare)
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Measurement of D*(+/-) meson production and determination of F-2(c(c)over-bar) at low Q(2) in deep-inelastic scattering at HERA
- 2011
-
Ingår i: European Physical Journal C. Particles and Fields. - : Springer Science and Business Media LLC. - 1434-6044. ; 71:10
-
Tidskriftsartikel (refereegranskat)abstract
- Inclusive production of D* mesons in deep-inelastic ep scattering at HERA is studied in the range 5 < Q(2) < 100 GeV2 of the photon virtuality and 0.02 < y < 0.7 of the inelasticity of the scattering process. The observed phase space for the D* meson is (pT) (D*) > 1.25 GeV and |eta( D*)| < 1.8. The data sample corresponds to an integrated luminosity of 348 pb(-1) collected with the H1 detector. Single and double differential cross sections are measured and the charm contribution F-2(c (c) over bar) to the proton structure function F-2 is determined. The results are compared to perturbative QCD predictions at next-to-leading order implementing different schemes for the charm mass treatment and with Monte Carlo models based on leading order matrix elements with parton showers.
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