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Inclusive dijet cross sections in neutral current deep inelastic scattering at HERA

European Physical Journal C 70:4 (2010) 965-982

Authors:

H Abramowicz, I Abt, L Adamczyk, M Adamus, R Aggarwal, S Antonelli, P Antonioli, A Antonov, M Arneodo, V Aushev, Y Aushev, O Bachynska, A Bamberger, AN Barakbaev, G Barbagli, G Bari, F Barreiro, D Bartsch, M Basile, O Behnke, J Behr, U Behrens, L Bellagamba, A Bertolin, S Bhadra, M Bindi, C Blohm, V Bokhonov, T Bołd, EG Boos, K Borras, D Boscherini, D Bot, SK Boutle, I Brock, E Brownson, R Brugnera, N Brümmer, A Bruni, G Bruni, B Brzozowska, PJ Bussey, JM Butterworth, B Bylsma, A Caldwell, M Capua, R Carlin, CD Catterall, S Chekanov, J Chwastowski, J Ciborowski, R Ciesielski, L Cifarelli, F Cindolo, A Contin, AM Cooper-Sarkar, N Coppola, M Corradi, F Corriveau, M Costa, G D'Agostini, F Dal Corso, J del Peso, RK Dementiev, S De Pasquale, M Derrick, RCE Devenish, D Dobur, BA Dolgoshein, G Dolinska, AT Doyle, V Drugakov, LS Durkin, S Dusini, Y Eisenberg, PF Ermolov, A Eskreys, S Fang, S Fazio, J Ferrando, MI Ferrero, J Figiel, M Forrest, B Foster, S Fourletov, G Gach, A Galas, E Gallo, A Garfagnini, A Geiser, I Gialas, LK Gladilin, D Gladkov, C Glasman, O Gogota, YA Golubkov, P Göttlicher, I Grabowska-Bołd, J Grebenyuk, I Gregor

Abstract:

Single- and double-differential inclusive dijet cross sections in neutral current deep inelastic ep scattering have been measured with the ZEUS detector using an integrated luminosity of 374 pb-1. The measurement was performed at large values of the photon virtuality, Q2, between 125 and 20 000 GeV2. The jets were reconstructed with the kT cluster algorithm in the Breit reference frame and selected by requiring their transverse energies in the Breit frame, ET,Bjet, to be larger than 8 GeV. In addition, the invariant mass of the dijet system, Mjj, was required to be greater than 20 GeV. The cross sections are described by the predictions of next-to-leading-order QCD. © 2010 The Author(s).
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Measurement of high-Q2 charged current deep inelastic scattering cross sections with a longitudinally polarised positron beam at HERA

European Physical Journal C 70:4 (2010) 945-963

Authors:

H Abramowicz, I Abt, L Adamczyk, M Adamus, R Aggarwal, S Antonelli, P Antonioli, A Antonov, M Arneodo, V Aushev, Y Aushev, O Bachynska, A Bamberger, AN Barakbaev, G Barbagli, G Bari, F Barreiro, D Bartsch, M Basile, O Behnke, J Behr, U Behrens, L Bellagamba, A Bertolin, S Bhadra, M Bindi, C Blohm, V Bokhonov, T Bołd, EG Boos, K Borras, D Boscherini, D Bot, SK Boutle, I Brock, E Brownson, R Brugnera, N Brümmer, A Bruni, G Bruni, B Brzozowska, PJ Bussey, JM Butterworth, B Bylsma, A Caldwell, M Capua, R Carlin, CD Catterall, S Chekanov, J Chwastowski, J Ciborowski, R Ciesielski, L Cifarelli, F Cindolo, A Contin, AM Cooper-Sarkar, N Coppola, M Corradi, F Corriveau, M Costa, G D'Agostini, F Dal Corso, J del Peso, RK Dementiev, S De Pasquale, M Derrick, RCE Devenish, D Dobur, BA Dolgoshein, G Dolinska, AT Doyle, V Drugakov, LS Durkin, S Dusini, Y Eisenberg, PF Ermolov, A Eskreys, S Fang, S Fazio, J Ferrando, MI Ferrero, J Figiel, M Forrest, B Foster, S Fourletov, G Gach, A Galas, E Gallo, A Garfagnini, A Geiser, I Gialas, LK Gladilin, D Gladkov, C Glasman, O Gogota, YA Golubkov, P Göttlicher, I Grabowska-Bołd, J Grebenyuk, I Gregor

Abstract:

Measurements of the cross sections for charged current deep inelastic scattering in e+p collisions with a longitudinally polarised positron beam are presented. The measurements are based on a data sample with an integrated luminosity of 132 pb-1 collected with the ZEUS detector at HERA at a centre-of-mass energy of 318 GeV. The total cross section is presented at positive and negative values of the longitudinal polarisation of the positron beams. The single-differential cross-sections dσ/dQ2, dσ/dx and dσ/dy are presented for Q2>200 GeV2. The reduced cross-section σ̃ is presented in the kinematic range 200
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All-optical steering of laser-wakefield-accelerated electron beams

Physical Review Letters 105:21 (2010)

Authors:

A Popp, J Vieira, J Osterhoff, Z Major, R Hörlein, M Fuchs, R Weingartner, TP Rowlands-Rees, M Marti, RA Fonseca, SF Martins, LO Silva, SM Hooker, F Krausz, F Grüner, S Karsch

Abstract:

We investigate the influence of a tilted laser-pulse-intensity front on laser-wakefield acceleration. Such asymmetric light pulses may be exploited to obtain control over the electron-bunch-pointing direction and in our case allowed for reproducible electron-beam steering in an all-optical way within an 8 mrad opening window with respect to the initial laser axis. We also discovered evidence of collective electron-betatron oscillations due to off-axis electron injection into the wakefield induced by a pulse-front tilt. These findings are supported by 3D particle-in-cell simulations. © 2010 The American Physical Society.
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Micron size laser-wire system at the ATF extraction line, recent results and ATF-II upgrade

Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment 623:1 (2010) 564-566

Authors:

A Aryshev, GA Blair, ST Boogert, G Boorman, A Bosco, L Corner, L Deacon, N Delerue, B Foster, F Gannaway, H Hayano, D Howell, P Karataev, L Nevay, M Newman, R Senanayake, N Terunuma, J Urakawa, R Walczak

Abstract:

The KEK Accelerator test facility (ATF) extraction line laser-wire system has been upgraded last year allowing the measurement of micron scale transverse size electron beams. The last measurements using the upgraded system from recent operation at the ATF are presented, demonstrating raw measurements of order 3μm RMS. The main component contributions to this measurement are also discussed. © 2010 Elsevier B.V. All rights reserved.
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First milestone on the path toward a table-top free-electron laser (FEL)

AIP Conference Proceedings 1228 (2010) 295-300

Authors:

M Fuchs, R Weingartner, A Popp, Z Major, S Becker, J Osterhoff, T Seggebrock, R Hörlein, GD Tsakiris, U Schramm, TP Rowlands-Rees, SM Hooker, D Habs, F Krausz, S Karsch, F Grüner

Abstract:

Latest developments in the field of laser-wakefield accelerators (LWFAs) have led to relatively stable electron beams in terms of peak energy, charge, pointing and divergence from mmsized accelerators. Simulations and LWFA theory indicate that these beams have low transverse emittances and ultrashort bunch durations on the order of ∼ 10 fs. These features make LWFAs perfectly suitable for driving high-brightness X-ray undulator sources and free-electron lasers (FELs) on a university-laboratory scale.With the detection of soft-X-ray radiation from an undulator source driven by laser-wakefield accelerated electrons, we succeeded in achieving a first milestone on this path. The source delivers remarkably stable photon beams which is mainly due to the stable electron beam and our miniature magnetic quadrupole lenses, which significantly reduce its divergence and angular shot-to-shot variation. An increase in electron energy allows for compact, tunable, hard-Xray undulator sources. Improvements of the electron beams in terms of charge and energy spread will put table-top FELs within reach. © 2010 American Institute of Physids.
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