Measurement of elastic electroproduction of mesons at HERA

Adloff, C.; Andreev, V.; Andrieu, Bernard; Arkadov, V.; Astvatsatourov, A.; Ayyaz, I.; Babaev, A.; Bähr, J.; Baranov, P.; Barrelet, E.; Bartel, W.; Bassler, U.; Bate, Pete S.; Beglarian, A.; Behnke, O.; Beier, C.; Belousov, A.; Benisch, T.; Berger, Ch.; Bernardi, G.; Berndt, T.; Bizot, J.C.; Borras, K.; Boudry, V.; Braunschweig, W.; Brisson, V.; Bröker, H.-B.; Brown, D.; Brückner, W.; Bruel, P.; Bruncko, D.; Bürger, J.; Büsser, F.W.; Bunyatyan, A.; Burkhardt, H.; Burrage, A.; Buschhorn, G.; Campbell, A.; Cao, Junpeng; Carli, T.; Caron, S.; Chabert, E. C.; Clarke, D.; Clerbaux, B.; Collard, C.; Contreras, J. G.; Coughlan, J. A.; Cousinou, M. C.; Cox, B.; Cozzika, G.; Cvach, J.; Dainton, J. B.; Dau, W.D.; Daum, K.; David, M.; Davidsson, Marcus; Delcourt, B.; Delerue, Nicolas; Demirchyan, R.; Roeck, A. De; Wolf, E. A. De; Diaconu, C.; Dixon, P.; Dodonov, V.; Dowell, J. D.; Droutskoi, A.; Duprel, C.; Eckerlin, G.; Eckstein, D.; Efremenko, V.; Egli, S.; Eichler, R.; Eisele, F.; Eisenhandler, E.; Ellerbrock, M.; Elsen, E.; Erdmann, M.; Erdmann, W.; Faulkner, Peter; Favart, L.; Fedotov, A.; Felst, R.; Ferencei, J.; Ferron, S.; Fleischer, M.; Flügge, G.; Fomenko, A.; Foresti, I.; Formánek, J.; Foster, J. M.; Franke, G.; Gabathuler, E.; Gabathuler, K.; Garvey, J.; Gassner, J.; Gayler, J.; Gerhards, R.; Ghazaryan, S.; Goerlich, L.; Gogitidze, N.; Goldberg, M.; Goodwin, Christopher J.; Grab, C.; Grässler, H.; Greenshaw, T.; Grindhammer, G.; Hadig, T.; Haidt, D.; Hajduk, L.; Haynes, W.J.; Heinemann, B.; Heinzelmann, G.; Henderson, R. C. W.; Hengstmann, S.; Henschel, H.; Heremans, R.; Herrera, G.; Herynek, I.; Hilgers, M.; Hiller, K. H.; Hladký, J.; Höting, P.; Hoffmann, D.; Hoprich, W.; Horisberger, R.; Hurling, S.; Ibbotson, M.; İşsever, Ç.; Jacquet, M.; Jaffré, M.; Janauschek, L.; Jansen, D. M.; Janssen, X.; Jemanov, V.; Jönsson, L.; Johnson, D.P.; Jones, M.; Jung, H.; Kästli, H.K.; Kant, D.; Kapichine, M.; Karlsson, Martin; Karschnick, O.; Kaufmann, O.; Kausch, M.; Keil, Frerich J.; Keller, N.; Kennedy, J.; Kenyon, I. R.; Kermiche, S.; Kiesling, C.; Klein, M.; Kleinwort, C.; Knies, G.; Koblitz, B.; Kolya, S. D.; Korbel, V.; Kostka, P.; Kotelnikov, S.K.; Krasny, M. W.; Krehbiel, H.; Kroseberg, J.; Krücker, D.; Krüger, K.; Küpper, A.; Kuhr, T.; Kurča, T.; Kutuev, R.Kh.; Lachnit, W.; Lahmann, R.; Lamb, David C.; Landon, M. P. J.; Lange, W.; Laštovička, T.; Lebedev, A.; Leißner, B.; Lemrani, R.; Lendermann, V.; Levonian, S.; Lindstroem, M.; Lobodzinska, E.; Łobodziński, B.; Loktionova, N.; Lubimov, V.; Lüders, S.; Lüke, D.; Lytkin, L.; Magnussen, N.; Mahlke-Krüger, H.; Malden, N.; Malinovski, E.; Malinovski, I.; Maraček, R.; Marage, P.; Marks, J.; Marshall, R.; Martyn, H. U.; Martyniak, J.; Maxfield, S. J.; Mehta, A.; Meier, K.; Merkel, P.; Metlica, F.; Meyer, H.; Meyer, J.; Meyer, P.-O.; Mikocki, S.; Milstead, D.; Mkrtchyan, T.; Mohr, R. Casanova; Mohrdieck, S.; Mondragón, M. N.; Moreau, F.; Morozov, A.; Morris, J. V.; Müller, K.; Мурін, П.; Nagovizin, V.; Naroska, B.; Naumann, J.; Naumann, T.; Nellen, G.; Newman, P. R.; Nicholls, T. C.; Niebergall, F.; Niebuhr, C.; Nix, O.; Nowak, G.; Nunnemann, T.; Olsson, J. E.; Ozerov, D.; Panassik, V.; Pascaud, C.; Patel, G. D.; Pérez, E.; Phillips, J. P.; Pitzl, D.; Pöschl, R.; Potachnikova, I.; Povh, Bogdan; Rabbertz, K.; Rädel, G.; Rauschenberger, J.; Reimer, P.; Reisert, B.; Reyna, D.; Rieß, S.; Rizvi, E.; Robmann, P.; Roosen, R.; Rostovtsev, A.; Royon, C.; Rusakov, S. V.; Rybicki, K.; Sankey, D. P. C.; Scheins, J.; Schilling, F. P.; Schleper, P.; Schmidt, D.; Schoeffel, L.; Schöning, A.; Schörner, T.; Schröder, V.; Schultz‐Coulon, H.‐C.; Sedlák, Kamil; Sefkow, F.; Shekelyan, V.; Sheviakov, I.; Shtarkov, L. N.; Siegmon, G.; Sievers, P.; Sirois, Y.; Sloan, T.; Smirnov, P.; Solochenko, V.; Soloviev, Y.; Spaskov, V.; Specka, A.; Spitzer, H.; Stamen, R.; Steinhart, J.; Stella, B.; Stellberger, A.; Stiewe, J.; Straumann, U.; Struczinski, W.; Swart, M.; Taševský, M.; Tchernyshov, V.; Tchetchelnitski, S.; Thompson, G.; Thompson, P. D.; Tobien, N.; Traynor, D.; Truöl, P.; Tsipolitis, G.; Turnau, J.; Turney, J.E.; Tzamariudaki, E.; Udluft, Steffen; Usik, A.; Valkár, Š.; Valkárová, A.; Vallée, C.; Mechelen, P. Van; Vazdik, Y.; Dombrowski, S. von; Wacker, K.; Wallny, R.; Walter, T.; Waugh, Benedict Martin; Weber, G.; Weber, M.; Wegener, D.; Wegner, A.; Wengler, T.; Werner, M.; White, G.; Wiesand, S.; Wilksen, T.; Winde, M.; Winter, G. G.; Wissing, C.; Wobisch, M.; Wollatz, H.; Wünsch, E.; Wyatt, A.; Žáček, J.; Zálešâk, J.; Zhang, Z.; Zhokin, A.; Zomer, F.; Zsembery, J.; Nedden, M. zur

doi:10.1016/s0370-2693(00)00613-4

Cited by 67 publications

(67 citation statements)

References 28 publications

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“…An immediate consequence of the cancellation of gluon and sea contributions to the unnatural parity amplitude is that σ U for φ production is very small, in fact compatible with zero. This is in agreement with the preliminary HERMES data [37] and with the H1 data [32]. Thus, there is indication from both theory and experiment that σ U for ρ and φ production is small.…”

Section: The Role Of Hsupporting

confidence: 92%

“…5 the handbag results on the ρ and φ cross sections are compared to experiment. Again good agreement with the H1 [25,32] and ZEUS [24,26,34] data is to be observed in a large range of Q 2 . The leading-twist contribution to these cross sections, i.e.…”

Section: Results On Cross Sectionssupporting

confidence: 73%

“…In a number of experiments [24,25,32,38,39] the SDMEs have been extracted from the measured decay angular distributions of the vector mesons. The formalism of the SDMEs, i.e.…”

Section: Results On Spin Density Matrix Elementsmentioning

confidence: 99%

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The role of the quark and gluon GPDs in hard vector-meson electroproduction

2007

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Electroproduction of light vector mesons is analyzed on the basis of handbag factorization. The required generalized parton distributions are constructed from the CTEQ6 parton distributions with the help of double distributions. The partonic subprocesses are calculated within the modified perturbative approach. The present work extends our previous analysis of the longitudinal cross section to the transverse one and other observables related to both the corresponding amplitudes. Our results are compared to recent experimental findings in detail.

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Section: The Role Of Hsupporting

confidence: 92%

Section: Results On Cross Sectionssupporting

confidence: 73%

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The role of the quark and gluon GPDs in hard vector-meson electroproduction

2007

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“…A systematic study of the dependence of forward di-pion azimuthal correlations on the PDF has been made using PYTHIA 6.222. Figure 3 shows the comparison between three different sets of parton distributions: the Duke-Owen set [17], which predates HERA data [18,19] and therefore does not include a rise in the gluon density at low-x, and the two sets CTEQ3L and CTEQ5L [20], the latter with a steeper rise of the gluon distribution at low-x. The right panel in Figure 3 shows the azimuthal correlations expected from these three PDF sets in p+p interactions.…”

Section: Systematicsmentioning

confidence: 99%

Two-particle correlations at forward rapidity in STAR

Braidot

2011

Nuclear Physics A

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During the 2008 run RHIC provided high luminosity in both p+p and d+Au collisions at √ s N N = 200 GeV. Electromagnetic calorimeter acceptance in STAR was enhanced by the new Forward Meson Spectrometer (FMS), and is now almost contiguous from −1 < η < 4 over the full azimuth. This large acceptance provides sensitivity to the gluon density in the nucleus down to x ≈ 10 −3 , as expected for 2 → 2 parton scattering. Measurements of the azimuthal correlation between a forward π 0 and an associated particle at large rapidity are sensitive to the low-x gluon density. Data exhibit the qualitative features expected from gluon saturation. A comparison to calculations using the Color Glass Condensate (CGC) model is presented.

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“…In general, the differential and total cross sections for ρ 0 -meson production by virtual photons are reasonably well described in the GPD-based approach of Refs. [15,16], not only at the high energies of the HERA collider experiments [20][21][22][23][24], but also at intermediate energies covered by the fixed-target experiments E665 [25] and HERMES [26].…”

Section: Introductionmentioning

confidence: 99%

Ratios of helicity amplitudes for exclusive $$\rho ^0$$ ρ 0 electroproduction on transversely polarized protons

et al. 2017

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Exclusive ρ 0 -meson electroproduction is studied by the HERMES experiment, using the 27.6 GeV longitudinally polarized electron/positron beam of HERA and a transversely polarized hydrogen target, in the kinematic region 1.0 GeV 2 < Q 2 < 7.0 GeV 2 , 3.0 GeV < W < 6.3 GeV, and −t < 0.4 GeV 2 . Using an unbinned maximum-likelihood method, 25 parameters are extracted. These determine the real and imaginary parts of the ratios of several helicity amplitudes describing ρ 0 -meson production by a virtual photon. The denominator of those ratios is the dominant amplitude, the nucleon-helicity-non-flip amplitude F 0 1 2 0 1 2 , which describes the production of a longitudinal ρ 0 -meson by a longitudinal virtual photon. The ratios of nucleon-helicity-nonflip amplitudes are found to be in good agreement with those from the previous HERMES analysis. The transverse target polarization allows for the first time the extraction of ratios of a number of nucleon-helicity-flip amplitudes to F 0 1 2 0 1 2 . Results obtained in a handbag approach based on generalized parton distributions taking into account the contribution from pion exchange are found to be in good agreement with these ratios. Within the model, the data favor a positive sign for the π − ρ transition form factor. By also exploiting the longitudinal beam polarization, a total of 71 ρ 0 spin-density matrix elements is determined from the extracted 25 parameters, in contrast to only 53 elements as directly determined in earlier analyses.

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Measurement of elastic electroproduction of mesons at HERA

Cited by 67 publications

References 28 publications

The role of the quark and gluon GPDs in hard vector-meson electroproduction

The role of the quark and gluon GPDs in hard vector-meson electroproduction

Two-particle correlations at forward rapidity in STAR

Ratios of helicity amplitudes for exclusive $$\rho ^0$$ ρ 0 electroproduction on transversely polarized protons

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