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201.
The production rates and substructure of jets have been studied in charged current deep inelastic e
+
p scattering for Q
2 > 200 GeV2 with the ZEUS detector at HERA using an integrated luminosity of 110.5 pb-1. Inclusive jet cross sections are presented for jets with transverse energies
GeV and pseudorapidities in the range
. Dijet cross sections are presented for events with a jet having
GeV and a second jet having
GeV. Measurements of the mean subjet multiplicity,
, of the inclusive jet sample are presented. Predictions based on parton-shower Monte Carlo models and next-to-leading-order QCD calculations are compared to the measurements. The value of
, determined from
at
for jets with
GeV, is
. The mean subjet multiplicity as a function of Q
2 is found to be consistent with that measured in NC DIS.Received: 5 June 2003, Published online: 10 October 2003 相似文献
202.
The HERA-B Collaboration I. Abt et al. 《The European Physical Journal C - Particles and Fields》2003,29(2):181-190
Inclusive differential cross sections and for the production of K
0
S
, , and particles are measured at HERA in proton-induced reactions on C, Al, Ti, and W targets. The incident beam energy is 920 GeV,
corresponding to GeV in the proton-nucleon system. The ratios of differential cross sections (K and are measured to be and , respectively, for xF . No significant dependence upon the target material is observed. Within errors, the slopes of the transverse momentum distributions
also show no significant dependence upon the target material. The dependence of the extrapolated total cross sections on the atomic mass A of the target material is discussed, and the deduced cross sections per nucleon are compared with results obtained at other energies.
Received: 16 December 2002 / Revised version: 6 March 2003 / Published online: 11 June 2003
RID="a"
ID="a" Supported by the Bundesministerium für Bildung und Forschung, FRG, under contract numbers 05-7BU35I, 05-7DO55P, 05
HB1HRA, 05 HB1KHA, 05 HB1PEA, 05 HB1PSA, 05 HB1VHA, 05 HB9HRA, 05 7HD15I, 05 7HH25I, 05 7MP25I, 05 7SI75I 相似文献
203.
For the first time at LEP the production of prompt photons is studied in the collisions of quasi-real photons using the OPAL data taken at
centre-of-mass energies between 183 GeV and 209 GeV. The total inclusive production cross-section for isolated prompt photons in the kinematic range of transverse momentum
GeV and pseudorapidity
is determined to be
. Differential cross-sections are compared to the predictions of a next-to-leading-order (NLO) calculation.Received: 6 May 2003, Published online: 4 November 2003 相似文献
204.
The inclusive e+p single and double differential cross sections for neutral and charged current processes are measured with the H1 detector at HERA. The data were taken in 1999 and 2000 at a centre-of-mass energy of
and correspond to an integrated luminosity of 65.2 pb-1. The cross sections are measured in the range of four-momentum transfer squared Q2 between 100 and
and Bjorken x between 0.0013 and 0.65. The neutral current analysis for the new e+p data and the earlier e-p data taken in 1998 and 1999 is extended to small energies of the scattered electron and therefore to higher values of inelasticity y, allowing a determination of the longitudinal structure function FL at high Q2 (
). A new measurement of the structure function
is obtained using
the new e+p and previously published
neutral current cross section data at high Q2. These data together with H1 low Q2 precision data are further used to perform new next-to-leading order QCD analyses in the framework of the Standard Model to extract flavour separated parton distributions in the proton.Arrival of the final proofs: 11 July 2003 相似文献
205.
Aoki S Fukugita M Hashimoto S Ishikawa KI Ishizuka N Iwasaki Y Kanaya K Kaneko T Kuramashi Y Okawa M Onogi T Tsutsui N Ukawa A Yamada N Yoshié T;JLQCD Collaboration 《Physical review letters》2003,91(21):212001
We present an unquenched lattice calculation for the B(0)-B(0) transition amplitude. The calculation, carried out at an inverse lattice spacing 1/a=2.22(4) GeV, incorporates two flavors of dynamical quarks described by the O(a)-improved Wilson fermion action and heavy quarks described by nonrelativistic QCD. Particular attention is paid to the uncertainty that arises from the chiral extrapolation, especially the effect of pion loops, for light quarks, which we find could be sizable for the leptonic decay constant, whereas it is small for the B parameters. We obtain f(B(d))=191(10)(+12-22) MeV, f(B(s))/f(B(d))=1.13(3)(+13-2), B(B(d))(m(b))=0.836(27)(+56-62), B(B(s))/B(B(d))=1.017(16)(+56-17), and xi=1.14(3)(+13-2), where the first error is statistical, and the second is systematic, including uncertainties due to chiral extrapolation, finite lattice spacing, heavy quark expansion, and perturbative operator matching. 相似文献
206.
Craig K Comfort JR Allgower CE Bekrenev V Berger E Briscoe WJ Clajus M Draper B Grosnick D Isenhower D Knecht N Koetke D Koulbardis A Kozlenko N Kruglov S Lolos GJ Lopatin I Manley DM Manweiler R Marusić A McDonald S Nefkens BM Olmsted J Papandreou Z Peaslee D Phaisangittisakul N Prakhov S Price JW Pulver M Ramirez AF Sadler ME Shafi A Spinka H Stanislaus S Starostin A Supek I Staudenmaier HM Tippens WB;Crystal Ball Collaboration 《Physical review letters》2003,91(10):102301
Data are presented for the reaction pi(-)p-->pi(0)pi(0)n in the range from threshold to p(pi(-))=750 MeV/c. The systematics of the data and multipole analyses are examined for sensitivity to a f(0)(600) ("sigma") meson. A one-pion-exchange mechanism is found to be very weak, or absent. The reaction appears to become dominated by sequential pi(0) decays through the Delta(1232) resonance as the beam momentum increases, along with substantial interference effects from several competing mechanisms. 相似文献
207.
Dillmann I Kratz KL Wöhr A Arndt O Brown BA Hoff P Hjorth-Jensen M Köster U Ostrowski AN Pfeiffer B Seweryniak D Shergur J Walters WB;ISOLDE Collaboration 《Physical review letters》2003,91(16):162503
First beta- and gamma-spectroscopic decay studies of the N=82 r-process "waiting-point" nuclide 130Cd have been performed at CERN/ISOLDE using the highest achievable isotopic selectivity. Several nuclear-physics surprises have been discovered. The first one is the unanticipatedly high energy of 2.12 MeV for the [pi g(9/2) multiply sign in circle nu g(7/2)] 1(+) level in 130In, which is fed by the main Gamow-Teller transition. The second surprise is the rather high Q(beta) value of 8.34 MeV, which is in agreement only with recent mass models that include the phenomenon of N=82 shell quenching. Possible implications of these new results on the formation of the A approximately 130 r-process abundance peak are presented. 相似文献
208.
Bauer F Bisplinghoff J Büsser K Busch M Colberg T Demirörs L Dahl C Eversheim PD Eyser O Felden O Gebel R Greiff J Hinterberger F Jonas E Krause H Lehmann C Lindlein J Maier R Meinerzhagen A Pauly C Prasuhn D Rohdjess H Rosendaal D von Rossen P Schirm N Scobel W Ulbrich K Weise E Wolf T Ziegler R;EDDA Collaboration 《Physical review letters》2003,90(14):142301
At the Cooler Synchrotron COSY/Jülich spin-correlation parameters in elastic proton-proton (pp) scattering have been measured with a 2.11 GeV polarized proton beam and a polarized hydrogen atomic beam target. We report results for A(NN), A(SS), and A(SL) for c.m. scattering angles between 30 degrees and 90 degrees. Our data on A(SS)--the first measurement of this observable above 800 MeV--clearly disagrees with predictions of available pp scattering phase-shift solutions while A(NN) and A(SL) are reproduced reasonably well. We show that in the direct reconstruction of the scattering amplitudes from the body of available pp elastic scattering data at 2.1 GeV the number of possible solutions is considerably reduced. 相似文献
209.
Measurement of helicity-dependent photoabsorption cross sections on the neutron from 815 to 1825 MeV
Dutz H Helbing K Krimmer J Speckner T Zeitler G Ahrens J Altieri S Annand JR Anton G Arends HJ Beck R Bock A Bradtke C Braghieri A v Drachenfels W Frommberger F Godo M Goertz S Grabmayr P Hasegawa S Hansen K Harmsen J Heid E Hillert W Holvoet H Horikawa N Iwata T Van Hoorebeke L d'Hose N Jennewein P Kiel B Klein F Kondratiev R Lang M Lannoy B Leukel R Lisin V Menze D Meyer W Michel T Naumann J Panzeri A Pedroni P Pinelli T Preobrajenski I Radtke E Reicherz G Rohlof C Rostomyan T Sauer M 《Physical review letters》2005,94(16):162001
Helicity-dependent total photoabsorption cross sections on the deuteron have been measured for the first time at ELSA (Bonn) in the photon energy range from 815 to 1825 MeV. Circularly polarized tagged photons impinging on a longitudinally polarized LiD target have been used together with a highly efficient 4pi detector system. The data around 1 GeV are not compatible with predictions from existing multipole analyses. From the measured energy range an experimental contribution to the GDH integral on the neutron of [33.9 +/- 5.5(stat) +/- 4.5(syst)] microb is extracted. 相似文献
210.
Madsen N Amoretti M Amsler C Bonomi G Bowe PD Carraro C Cesar CL Charlton M Doser M Fontana A Fujiwara MC Funakoshi R Genova P Hangst JS Hayano RS Jørgensen LV Kellerbauer A Lagomarsino V Landua R Lodi-Rizzini E Macri M Mitchard D Montagna P Pruys H Regenfus C Rotondi A Testera G Variola A Venturelli L van der Werf DP Yamazaki Y Zurlo N;ATHENA Collaboration 《Physical review letters》2005,94(3):033403
Antihydrogen is formed when antiprotons are mixed with cold positrons in a nested Penning trap. We present experimental evidence, obtained using our antihydrogen annihilation detector, that the spatial distribution of the emerging antihydrogen atoms is independent of the positron temperature and axially enhanced. This indicates that antihydrogen is formed before the antiprotons are in thermal equilibrium with the positron plasma. This result has important implications for the trapping and spectroscopy of antihydrogen. 相似文献