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41.
Multijet production rates in neutral current deep inelastic scattering have been measured in the range of exchanged boson
virtualities
. The data were taken at the ep collider HERA with centre-of-mass energy
using the ZEUS detector and correspond to an integrated luminosity of
. Jets were identified in the Breit frame using the kT cluster algorithm in the longitudinally invariant inclusive mode. Measurements of differential dijet and trijet cross sections
are presented as functions of jet transverse energy (
), pseudorapidity (
) and Q2 with
and
. Next-to-leading-order QCD calculations describe the data well. The value of the strong coupling constant
, determined from the ratio of the trijet to dijet cross sections, is
.
Received: 1 April 2005, Revised: 28 June 2005, Published online: 30 August 2005 相似文献
42.
The H Collaboration 《The European Physical Journal C - Particles and Fields》2005,38(4):437-445
Results are presented on the photoproduction of isolated prompt photons, inclusively and associated with jets, in the
center of mass energy range 142 < W < 266 GeV. The cross sections are measured for the transverse momentum range of the photons
GeV and for associated jets with E
T
jet > 4.5 GeV. They are measured differentially as a function of
, the pseudorapidities
and
and estimators of the momentum fractions
and x
p
of the incident photon and proton carried by the constituents participating in the hard process. In order to further investigate the underlying dynamics, the angular correlation between the prompt photon and the jet in the transverse plane is studied. Predictions by perturbative QCD calculations in next to leading order are about
below the inclusive prompt photon data after corrections for hadronisation and multiple interactions, but are in reasonable agreement with the results for prompt photons associated with jets. Comparisons with the predictions of the event generators PYTHIA and HERWIG are also presented.Received: 13 July 2004, Revised: 15 November 2004, Published online: 17 December 2004 相似文献
43.
Jørgensen LV Amoretti M Bonomi G Bowe PD Canali C Carraro C Cesar CL Charlton M Doser M Fontana A Fujiwara MC Funakoshi R Genova P Hangst JS Hayano RS Kellerbauer A Lagomarsino V Landua R Lodi Rizzini E Macrì M Madsen N Mitchard D Montagna P Rotondi A Testera G Variola A Venturelli L van der Werf DP Yamazaki Y;ATHENA Collaboration 《Physical review letters》2005,95(2):025002
We have developed a new method, based on the ballistic transfer of preaccumulated plasmas, to obtain large and dense positron plasmas in a cryogenic environment. The method involves transferring plasmas emanating from a region with a low magnetic field (0.14 T) and relatively high pressure (10(-9) mbar) into a 15 K Penning-Malmberg trap immersed in a 3 T magnetic field with a base pressure better than 10(-13) mbar. The achieved positron accumulation rate in the high field cryogenic trap is more than one and a half orders of magnitude higher than the previous most efficient UHV compatible scheme. Subsequent stacking resulted in a plasma containing more than 1.2 x 10(9) positrons, which is a factor 4 higher than previously reported. Using a rotating wall electric field, plasmas containing about 20 x 10(6) positrons were compressed to a density of 2.6 x 10(10) cm(-3). This is a factor of 6 improvement over earlier measurements. 相似文献
44.
Agnello M Beer G Benussi L Bertani M Bianco S Botta E Bressani T Busso L Calvo D Camerini P Cerello P Dalena B De Mori F D'Erasmo G Di Santo D Fabbri FL Faso D Feliciello A Filippi A Filippini V Fiore EM Fujioka H Gianotti P Grion N Lucherini V Marcello S Maruta T Mirfakhrai N Morra O Nagae T Olin A Outa H Pace E Palomba M Pantaleo A Panzarasa A Paticchio V Piano S Pompili F Rui R Simonetti G So H Tomassini S Toyoda A Wheadon R Zenoni A;FINUDA Collaboration 《Physical review letters》2005,94(21):212303
We have searched for a deeply bound kaonic state by using the FINUDA spectrometer installed at the e(+)e(-) collider DAPhiNE. Almost monochromatic K(-)'s produced through the decay of phi(1020) mesons are used to observe K(-) absorption reactions stopped on very thin nuclear targets. Taking this unique advantage, we have succeeded to detect a kaon-bound state K(-)pp through its two-body decay into a Lambda hyperon and a proton. The binding energy and the decay width are determined from the invariant-mass distribution as 115(+6)(-5)(stat)(+3)(-4)(syst) MeV and 67(+14)(-11)(stat)(+2)(-3)(syst) MeV, respectively. 相似文献
45.
Wahl U Rita E Correia JG Marques AC Alves E Soares JC;ISOLIDE Collaboration 《Physical review letters》2005,95(21):215503
Arsenic has been reported in the literature as one of the few p-type dopants in the technologically promising II-VI semiconductor ZnO. However, there is an ongoing debate whether the p-type character is due to As simply replacing O atoms or to the formation of more complicated defect complexes, possibly involving As on Zn sites. We have determined the lattice location of implanted As in ZnO by means of conversion-electron emission channeling from radioactive (73)As. In contrast to what one might expect from its nature as a group V element, we find that As does not occupy substitutional O sites but in its large majority substitutional Zn sites. Arsenic in ZnO (and probably also in GaN) is thus an interesting example for an impurity in a semiconductor where the major impurity lattice site is determined by atomic size and electronegativity rather than its position in the periodic system. 相似文献
46.
We report on a high statistics search for the Ξ??(1860) resonance in Σ?-nucleus collisions at 340 GeV/c. No evidence for this resonance is found in our data sample which contains 676000 Ξ? candidates above bakground. For the decay channel Ξ??(1860)→Ξ? π ? and the kinematic range 0.15<xF<0.9 we find a 3σ upper limit for the production cross section of 3.1 and 3.5 μb per nucleon, for reactions with carbon and copper, respectively. 相似文献
47.
Aubin C Bernard C Detar C Di Pierro M Freeland ED Gottlieb S Heller UM Hetrick JE El-Khadra AX Kronfeld AS Levkova L Mackenzie PB Menscher D Maresca F Nobes M Okamoto M Renner D Simone J Sugar R Toussaint D Trottier HD;Fermilab Lattice Collaboration;MILC Collaboration;HPQCD Collaboration 《Physical review letters》2005,95(12):122002
We present the first lattice QCD calculation with realistic sea quark content of the D+-meson decay constant f(D+). We use the MILC Collaboration's publicly available ensembles of lattice gauge fields, which have a quark sea with two flavors (up and down) much lighter than a third (strange). We obtain f(D+)=201+/-3+/-17 MeV, where the errors are statistical and a combination of systematic errors. We also obtain f(Ds)=249+/-3+/-16 MeV for the Ds meson. 相似文献
48.
Baggio L Bignotto M Bonaldi M Cerdonio M Conti L De Rosa M Falferi P Fortini P Inguscio M Liguori N Marin F Mezzena R Mion A Ortolan A Prodi GA Poggi S Salemi F Soranzo G Taffarello L Vedovato G Vinante A Vitale S Zendri JP;AURIGA Collaboration 《Physical review letters》2005,95(8):081103
At the time when the giant flare of SGR1806-20 occurred, the AURIGA "bar" gravitational-wave (GW) detector was on the air with a noise performance close to stationary Gaussian. This allows us to set relevant upper limits, at a number of frequencies in the vicinities of 900 Hz, on the amplitude of the damped GW wave trains, which, according to current models, could have been emitted, due to the excitation of normal modes of the star associated with the peak in x-ray luminosity. 相似文献
49.
Reisdorf W Andronic A Gobbi A Hartmann ON Herrmann N Hildenbrand KD Kim YJ Kirejczyk M Koczoń P Kress T Leifels Y Schüttauf A Tymiński Z Xiao ZG Alard JP Barret V Basrak Z Bastid N Benabderrahmane ML Caplar R Crochet P Dupieux P Dzelalija M Fodor Z Grishkin Y Hong B Kecskemeti J Korolija M Kotte R Lebedev A Lopez X Merschmeyer M Mösner J Neubert W Pelte D Petrovici M Rami F de Schauenburg B Seres Z Sikora B Sim KS Simion V Siwek-Wilczyńska K Smolyankin V Stockmeier M Stoicea G Wagner P 《Physical review letters》2004,92(23):232301
We present a complete systematics (excitation functions and system-size dependences) of global stopping and side flow for heavy ion reactions in the energy range between 0.09A and 1.93A GeV. For the heaviest system, Au+Au, we observe a plateau of maximal stopping extending from about 0.2A to 0.8A GeV with a fast drop on both sides. The degree of stopping, which is shown to remain significantly below the expectations of a full stopping scenario, is found to be highly correlated to the amount of side flow. 相似文献
50.
Auerbach LB Burman RL Caldwell DO Church ED Cochran AK Donahue JB Fazely AR Garvey GT Gunasingha RM Imlay RL Kahrimanis G Louis WC Majkic R Malik A McIlhany KL Metcalf WJ Mills GB Rupnik D Sandberg VD Smith D Somodi RF Stancu I Strossman WD Sung M Tayloe R VanDalen GJ Vernon W Wadia N White DH Yellin S Yi H;LSND Collaboration 《Physical review letters》2004,92(9):091801
We observe a net beam excess of 8.7+/-6.3(stat)+/-2.4(syst) events, above 160 MeV, resulting from the charged-current reaction of nu(micro) and/or nu;(mu) on C and H in the LSND detector. No beam-related muon background is expected in this energy regime. Within an analysis framework of pi(0)-->nu(mu)nu;(mu), we set a direct upper limit for this branching ratio of Gamma(pi(0)-->nu(mu)nu;(mu))/Gamma(pi(0)-->all)<1.6 x 10(-6) at 90% confidence level. 相似文献