The helicity structure of the diffractive electroproducti on of mesons, e+ p ! e+ + Y , is studied in a previously unexplored region of large four-m omentum transfer squared at the proton vertex,t: 0 < t < 3 G eV , wheret = jtj jtjm in . The data used are collected with the H1 detector at HERA in the kinematic domai n 2:5 < Q 2 < 60 G eV , 40 < W < 120 GeV. Notdependence of the r 00 spin density matrix element is found. A significanttdependent helicity non-conservation from the virtual phot on to the meson is observed for the spin density matrix element combination s r 00 + 2r 11 andr 00 + 2r 11 . Thesetdependences are consistently described by a perturbative Q CD model based on the exchange of two gluons. C. Adloff, V. Andreev, B. Andrieu, T. Anthonis, V. Arkadov, A. Astvatsatourov , A. Babaev, J. Bähr , P. Baranov , E. Barrelet , W. Bartel, J. Becker , A. Beglarian, O. Behnke, C. Beier, A. Belousov, Ch. Berger , T. Berndt, J.C. Bizot , J. Böhme, V. Boudry, W. Braunschweig , V. Brisson, H.-B. Bröker, D.P. Brown, W. Brückner , D. Bruncko, J. Bürger , F.W. Büsser , A. Bunyatyan, A. Burrage, G. Buschhorn , L. Bystritskaya, A.J. Campbell , J. Cao, S. Caron, F. Cassol-Brunner , D. Clarke, B. Clerbaux, C. Collard, J.G. Contreras , Y.R. Coppens , J.A. Coughlan, M.-C. Cousinou, B.E. Cox, G. Cozzika, J. Cvach, J.B. Dainton, W.D. Dau, K. Daum, M. Davidsson, B. Delcourt, N. Delerue, R. Demirchyan, A. De Roeck, E.A. De Wolf, C. Diaconu, J. Dingfelder , P. Dixon, V. Dodonov, J.D. Dowell, A. Droutskoi, A. Dubak, C. Duprel , G. Eckerlin, D. Eckstein, V. Efremenko, S. Egli, R. Eichler, F. Eisele, E. Eisenhandler , M. Ellerbrock, E. Elsen, M. Erdmann, W. Erdmann, P.J.W. Faulkner , L. Favart, A. Fedotov, R. Felst , J. Ferencei , S. Ferron, M. Fleischer , Y.H. Fleming, G. Flügge, A. Fomenko, I. Foresti , J. Formánek , G. Franke, E. Gabathuler , K. Gabathuler , J. Garvey, J. Gassner , J. Gayler , R. Gerhards , C. Gerlich, S. Ghazaryan , L. Goerlich, N. Gogitidze, C. Grab, V. Grabski , H. Grässler , T. Greenshaw, G. Grindhammer , T. Hadig, D. Haidt, L. Hajduk, J. Haller, W.J. Haynes , B. Heinemann, G. Heinzelmann , R.C.W. Henderson , S. Hengstmann , H. Henschel , R. Heremans , G. Herrera, I. Herynek, M. Hildebrandt , M. Hilgers, K.H. Hiller, J. Hladký, P. Höting, D. Hoffmann, R. Horisberger , A. Hovhannisyan , S. Hurling, M. Ibbotson, Ç. İşsever , M. Jacquet , M. Jaffre, L. Janauschek , X. Janssen , V. Jemanov, L. Jönsson , C. Johnson , D.P. Johnson , M.A.S. Jones , H. Jung, D. Kant, M. Kapichine, M. Karlsson, O. Karschnick, F. Keil, N. Keller, J. Kennedy, I.R. Kenyon, S. Kermiche, C. Kiesling, P. Kjellberg, M. Klein, C. Kleinwort, T. Kluge, G. Knies, B. Koblitz, S.D. Kolya, V. Korbel, P. Kostka, S.K. Kotelnikov, R. Koutouev, A. Koutov, H. Krehbiel , J. Kroseberg , K. Krüger, A. Küpper, T. Kuhr, T. Kurča, D. Lamb, M.P.J. Landon , W. Lange, T. Laštovička, P. Laycock, E. Lebailly, A. Lebedev, B. Leißner , R. Lemrani , V. Lendermann, S. Levonian, M. Lindstroem, B. List, E. Lobodzinska , B. Lobodzinski , A. Loginov, N. Loktionova, V. Lubimov, S. Lüders, D. Lüke, L. Lytkin, H. Mahlke-Krüger , N. Malden, E. Malinovski, I. Malinovski, R. Maraček, P. Marage, J. Marks, R. Marshall , H.-U. Martyn, J. Martyniak, S.J. Maxfield, D. Meer, A. Mehta, K. Meier, A.B. Meyer, H. Meyer, J. Meyer , P.-O. Meyer , S. Mikocki, D. Milstead, T. Mkrtchyan, R. Mohr, S. Mohrdieck, M.N. Mondragon, F. Moreau, A. Morozov, J.V. Morris, K. Müller, P. Murı́n, V. Nagovizin, B. Naroska, J. Naumann , Th. Naumann , G. Nellen, P.R. Newman , F. Niebergall , C. Niebuhr , O. Nix, G. Nowak, J.E. Olsson , D. Ozerov, V. Panassik , C. Pascaud , G.D. Patel , M. Peez, E. Perez , J.P. Phillips, D. Pitzl, R. Pöschl , I. Potachnikova, B. Povh, G. Rädel , J. Rauschenberger , P. Reimer , B. Reisert , D. Reyna, C. Risler, E. Rizvi, P. Robmann , R. Roosen, A. Rostovtsev , S. Rusakov , K. Rybicki, D.P.C. Sankey , S. Schätzel , J. Scheins , F.-P. Schilling, P. Schleper , D. Schmidt , D. Schmidt , S. Schmidt , S. Schmitt , M. Schneider , L. Schoeffel , A. Schöning, T. Schörner , V. Schröder , H.-C. Schultz-Coulon , C. Schwanenberger , K. Sedlák, F. Sefkow, V. Shekelyan, I. Sheviakov, L.N. Shtarkov, Y. Sirois, T. Sloan, P. Smirnov, Y. Soloviev, D. South, V. Spaskov, A. Specka, H. Spitzer ,

Measurements of cross sections for events with charm and beauty jets in deep inelastic scattering at HERA are presented. Events with jets of transverse energy E_T^jet > 6 GeV and pseudorapidity -1.0 < eta^jet < 1.5 in the laboratory frame are selected in the kinematic region of photon virtuality Q^2 > 6 GeV^2 and inelasticity variable 0.07 < y < 0.625. Measurements are also made requiring a jet in the Breit frame with E_T^*jet > 6 GeV. The data were collected with the H1 detector in the years 2006 and 2007 corresponding to an integrated luminosity of 189 pb^-1. The numbers of charm and beauty jets are determined using variables reconstructed using the H1 vertex detector with which the impact parameters of the tracks to the primary vertex and the position of secondary vertices are measured. The measurements are compared with QCD predictions and with previous measurements where heavy flavours are identified using muons.

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).

Inclusive charm and beauty cross sections are measured in e − p and e + p neutral current collisions at HERA in the kinematic region of photon virtuality 5≤Q 2≤2000 GeV2 and Bjorken scaling variable 0.0002≤x≤0.05. The data were collected with the H1 detector in the years 2006 and 2007 corresponding to an integrated luminosity of 189 pb−1. The numbers of charm and beauty events are determined using variables reconstructed by the H1 vertex detector including the impact parameter of tracks to the primary vertex and the position of the secondary vertex. The measurements are combined with previous data and compared to QCD predictions.

Diffractive electroproduction of ρ and ϕ mesons is measured at HERA with the H1 detector in the elastic and proton dissociative channels. The data correspond to an integrated luminosity of 51 pb−1. About 10500 ρ and 2000 φ events are analysed in the kinematic range of squared photon virtuality 2.5 ≤ Q 2 ≤ 60 GeV2, photon-proton centre of mass energy 35 ≤ W ≤ 180 GeV and squared four-momentum transfer to the proton |t| ≤ 3 GeV2. The total, longitudinal and transverse cross sections are measured as a function of Q 2, W and |t|. The measurements show a transition to a dominantly “hard” behaviour, typical of high gluon densities and small \( q\overline q \) dipoles, for Q 2 larger than 10 to 20 GeV2. They support flavour independence of the diffractive exchange, expressed in terms of the scaling variable (Q 2+M 2 V )/4, and proton vertex factorisation. The spin density matrix elements are measured as a function of kinematic variables. The ratio of the longitudinal to transverse cross sections, the ratio of the helicity amplitudes and their relative phases are extracted. Several of these measurements have not been performed before and bring new information on the dynamics of diffraction in a QCD framework. The measurements are discussed in the context of models using generalised parton distributions or universal dipole cross sections.

A measurement is presented of inelastic photo- and electroproduction of J / ψ mesons in ep scattering at HERA. The data were recorded with the H1 detector in the period from 2004 to 2007. Single and double differential cross sections are determined and the helicity distributions of the J / ψ mesons are analysed. The results are compared to theoretical predictions in the colour singlet model and in the framework of non-relativistic QCD. Calculations in the colour singlet model using a k T factorisation ansatz are able to give a good description of the data, while colour singlet model calculations to next-to-leading order in collinear factorisation underestimate the data.

A measurement of prompt photons in photoproduction in ep collisions with the H1 detector is presented. The analysis is based on data taken in the years 2004-2007, corresponding to a total integrated luminosity of 340 pb -1. The photon signal is extracted using a multivariate analysis based on cluster calorimeter shower shape variables. Inclusive and exclusive cross sections are presented as a function of the transverse energy EγT in the range 5 to 15 GeV and the pseudorapidity ηγ range -1.0 to 2.4. The momentum fractions xγ and xproton of the incident photon and proton respectively carried by the constituents participating in the hard scattering process are measured as well. The results are compared to predictions from theoretical calculations.

The production of jets is studied in deep-inelastic e + p scattering at low negative four momentum transfer squared 5<Q 2<100 GeV2 and at inelasticity 0.2<y<0.7 using data recorded by the H1 detector at HERA in the years 1999 and 2000, corresponding to an integrated luminosity of 43.5 pb−1. Inclusive jet, 2-jet and 3-jet cross sections as well as the ratio of 3-jet to 2-jet cross sections are measured as a function of Q 2 and jet transverse momentum. The 2-jet cross section is also measured as a function of the proton momentum fraction ξ. The measurements are well described by perturbative quantum chromodynamics at next-to-leading order corrected for hadronisation effects and are subsequently used to extract the strong coupling α s .

The inclusive production of D*(2010) mesons in deep-inelastic ep scattering is measured in the kinematic region of photon virtuality 100 < Q^2 < 1000 GeV^2 and inelasticity 0.02 < y < 0.7. Single and double differential cross sections for inclusive D* meson production are measured in the visible range defined by |eta(D*)| < 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.

A first measurement is presented of the charge asymmetry in the hadronic final state from the hard interaction in deep-inelastic ep neutral current scattering at HERA. The measurement is performed in the range of negative squared four momentum transfer 100 < Q(2) < 8000 GeV2. The difference between the event normalised distributions of the scaled momentum, x(p), for positively and negatively charged particles, measured in the current region of the Breit frame, is studied together with its evolution as a function of Q. The results are compared to Monte Carlo models at the hadron and parton levels. (C) 2009 Elsevier B.V. All rights reserved.

The process of charm quark fragmentation is studied using D * ± meson production in deep-inelastic scattering as measured by the H1 detector at HERA. The parameters of fragmentation functions are extracted for QCD models based on leading order matrix elements and DGLAP or CCFM evolution of partons together with string fragmentation and particle decays. Additionally, they are determined for a next-to-leading order QCD calculation in the fixed flavour number scheme using the independent fragmentation of charm quarks to D * ± mesons. Two different regions of phase space are investigated defined by the presence or absence of a jet containing the D * ± meson in the event. The fragmentation parameters extracted for the two phase space regions are found to be different.

The process of charm quark fragmentation is studied using D * ± meson production in deep-inelastic scattering as measured by the H1 detector at HERA. The parameters of fragmentation functions are extracted for QCD models based on leading order matrix elements and DGLAP or CCFM evolution of partons together with string fragmentation and particle decays. Additionally, they are determined for a next-to-leading order QCD calculation in the fixed flavour number scheme using the independent fragmentation of charm quarks to D * ± mesons. Two different regions of phase space are investigated defined by the presence or absence of a jet containing the D * ± meson in the event. The fragmentation parameters extracted for the two phase space regions are found to be different. Eur. Phys. J. C (2009) 59: 589–606 DOI 10.1140/epjc/s10052-008-0792-2 Regular Article Experimental Physics Study of charm fragmentation into D∗± mesons in deep-inelastic scattering at HERA

A model-independent search for deviations from the Standard Model prediction is performed in $e^+ p$ and $e^- p$ collisions at HERA II using all high energy data recorded by the H1 experiment. This corresponds to a total integrated luminosity of 337 pb$^{-1}$. All event topologies involving isolated electrons, photons, muons, neutrinos and jets with high transverse momenta are investigated in a single analysis. Events are assigned to exclusive classes according to their final state. A statistical algorithm is used to search for deviations from the Standard Model in distributions of the scalar sum of transverse momenta or invariant mass of final state particles and to quantify their significance. A good agreement with the Standard Model prediction is observed in most of the event classes. The most siginificant deviation is found in the \mujnp channel in $e^+p$ collisions.

The first measurement of diffractive scattering of quasi-real photons with large momentum transfer gamma p -> gamma Y, where Y is the proton dissociative system, is made using the H1 detector at HERA. The measurement is performed for initial photon virtualities Q^2 < 0.01 GeV^2. Cross sections are measured as a function of W, the incident photon-proton entre of mass energy, and t, the square of the four-momentum transferred at the proton vertex, in the range 175 < W < 247 GeV and 4<|t|<36 GeV^2. The W dependence is well described by a model based on perturbative QCD using a leading logarithmic approximation of the BFKL evolution. The measured |t| dependence is harder than that predicted by the model and those observed in exclusive vector meson production.

A measurement of the inclusive deep-inelastic neutral current e+p scattering cross section is reported in the region of four-momentum transfer squared, 12<=Q^2<=150 GeV^2, and Bjorken x, 2x10^-4<=x<=0.1. The results are based on data collected by the H1 Collaboration at the ep collider HERA at positron and proton beam energies of E_e=27.6 GeV and E_p=920 GeV, respectively. The data are combined with previously published data, taken at E_p=820 GeV. The accuracy of the combined measurement is typically in the range of 1.3-2%. A QCD analysis at next-to-leading order is performed to determine the parton distributions in the proton based on H1 data.

A measurement of the inclusive ep scattering cross section is presented in the region of low momentum transfers, 0.2 GeV^2 < Q^2 < 12 GeV^2, and low Bjorken x, 5x10^-6 < x < 0.02. The result is based on two data sets collected in dedicated runs by the H1 Collaboration at HERA at beam energies of 27.6 GeV and 920 GeV for positrons and protons, respectively. A combination with data previously published by H1 leads to a cross section measurement of a few percent accuracy. A kinematic reconstruction method exploiting radiative ep events extends the measurement to lower Q^2 and larger x. The data are compared with theoretical models which apply to the transition region from photoproduction to deep inelastic scattering.

Aaron, F D; Alexa, C; Andreev, V; Antunovic, B; Aplin, S; Müller, K; Nowak, K; Robmann, P; Schmitz, C; Schöning, A; Straumann, U; Truöl, P Aaron, F D; Alexa, C; Andreev, V; Antunovic, B; Aplin, S; Müller, K; Nowak, K; Robmann, P; Schmitz, C; Schöning, A; Straumann, U; Truöl, P (2009). Events with isolated leptons and missing transverse momentum and measurement of W production at HERA. The European Physical Journal C, 64(2):251-271. Postprint available at: http://www.zora.uzh.ch

The inclusive production of D(2010) mesons in deep-inelastic ep scattering is measured in the kinematic region of photon virtuality 100 < Q2 < 1000GeV and inelasticity 0.02 < y < 0.7. Single and double differential cross sections for inclusive D meson production are measured in the visible range defined by |η(D∗)| < 1.5 and pT (D ) > 1.5GeV. 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 cc̄ 2 , to the proton structure function F2 is determined. The measurements are compared with QCD predictions. Submitted to Phys. Lett. B Dedicated to the memory of our dear friend and colleague, Beate Naroska F.D. Aaron, C. Alexa, K. Alimujiang, V. Andreev, B. Antunovic, S. Backovic, A. Baghdasaryan, E. Barrelet, W. Bartel, K. Begzsuren, A. Belousov, J.C. Bizot, V. Boudry, I. Bozovic-Jelisavcic, J. Bracinik, G. Brandt, M. Brinkmann, V. Brisson, D. Bruncko, A. Bunyatyan, G. Buschhorn, L. Bystritskaya, A.J. Campbell, K.B. Cantun Avila, K. Cerny, V. Cerny, V. Chekelian, A. Cholewa, J.G. Contreras, J.A. Coughlan, G. Cozzika, J. Cvach, J.B. Dainton, K. Daum, M. Deák, B. Delcourt, J. Delvax, E.A. De Wolf, C. Diaconu, V. Dodonov, A. Dossanov, A. Dubak, G. Eckerlin, V. Efremenko, S. Egli, A. Eliseev, E. Elsen, A. Falkiewicz, L. Favart, A. Fedotov, R. Felst, J. Feltesse, J. Ferencei, D.-J. Fischer, M. Fleischer, A. Fomenko, E. Gabathuler, J. Gayler, S. Ghazaryan, A. Glazov, I. Glushkov, L. Goerlich, N. Gogitidze, M. Gouzevitch, C. Grab, T. Greenshaw, B.R. Grell, G. Grindhammer, S. Habib, D. Haidt, C. Helebrant, R.C.W. Henderson, E. Hennekemper, H. Henschel, M. Herbst, G. Herrera, M. Hildebrandt, K.H. Hiller, D. Hoffmann, R. Horisberger, T. Hreus, M. Jacquet, X. Janssen, L. Jönsson, A.W. Jung, H. Jung, M. Kapichine, J. Katzy, I.R. Kenyon, C. Kiesling, M. Klein, C. Kleinwort, T. Kluge, A. Knutsson, R. Kogler, P. Kostka, M. Kraemer, K. Krastev, J. Kretzschmar, A. Kropivnitskaya, K. Krüger, K. Kutak, M.P.J. Landon, W. Lange, G. Laštovička-Medin, P. Laycock, A. Lebedev, V. Lendermann, S. Levonian, G. Li, K. Lipka, A. Liptaj, B. List, J. List, N. Loktionova, R. Lopez-Fernandez, V. Lubimov, A. Makankine, E. Malinovski, P. Marage, Ll. Marti, H.-U. Martyn, S.J. Maxfield, A. Mehta, A.B. Meyer, H. Meyer, H. Meyer, J. Meyer, S. Mikocki, I. Milcewicz-Mika, F. Moreau, A. Morozov, J.V. Morris, M.U. Mozer, M. Mudrinic, K. Müller, P. Murı́n, Th. Naumann, P.R. Newman, C. Niebuhr, A. Nikiforov, D. Nikitin, G. Nowak, K. Nowak, J.E. Olsson, S. Osman, D. Ozerov, P. Pahl, V. Palichik, I. Panagoulias, M. Pandurovic, Th. Papadopoulou, C. Pascaud, G.D. Patel, O. Pejchal, E. Perez, A. Petrukhin, I. Picuric, S. Piec, D. Pitzl, R. Plačakytė, B. Pokorny, R. Polifka, B. Povh, V. Radescu, A.J. Rahmat, N. Raicevic, A. Raspiareza, T. Ravdandorj, P. Reimer, E. Rizvi, P. Robmann, B. Roland, R. Roosen, A. Rostovtsev, M. Rotaru, J.E. Ruiz Tabasco, S. Rusakov, D. Šálek, D.P.C. Sankey, M. Sauter, E. Sauvan, S. Schmitt, L. Schoeffel, A. Schöning, H.-C. Schultz-Coulon, F. Sefkow, R.N. Shaw-West, L.N. Shtarkov, S. Shushkevich, T. Sloan, I. Smiljanic, Y. Soloviev, P. Sopicki, D. South, V. Spaskov, A. Specka, Z. Staykova, M. Steder, B. Stella, G. Stoicea, U. Straumann, D. Sunar, T. Sykora, V. Tchoulakov, G. Thompson, P.D. Thompson, T. Toll, F. Tomasz, T.H. Tran, D. Traynor, T.N. Trinh, P. Truöl, I. Tsakov, B. Tseepeldorj, J. Turnau, K. Urban, A. Valkárová, C. Vallée, P. Van Mechelen, A. Vargas Trevino, Y. Vazdik, S. Vinokurova, V. Volchinski, M. von den Driesch, D. Wegener, Ch. Wissing, E. Wünsch, J. Žáček, J. Zálešák, Z. Zhang, A. Zhokin, T. Zimmermann, H. Zohrabyan, and F. Zomer 1 I. Physikalisches Institut der RWTH, Aachen, Germany 2 Vinca Institute of Nuclear Sciences, Belgrade, Serbia 3 School of Physics and Astronomy, University of Birmingham, Birmingham, UK 4 Inter-University Institute for High Energies ULB-VUB, Brussels and Universiteit Antwerpen, Antwerpen, Belgium