摘要:

I describe the future accelerator facilities that are currently foreseen for electroweak scale physics, neutrino physics, and nuclear structure. I will explore the physics justification for these machines, and suggest how the case for future accelerators can be made. © 2004 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1664202

出版商:AIP    

年代:1904

数据来源: AIP

摘要:

The NuTeV experiment at Fermilab obtained pure high statistics samples of neutrino and antineutrino interactions using its sign‐selected beam. Preliminary inclusive charged current differential cross sections of neutrino and antineutrino interactions on iron are presented, along with preliminary measurements ofF2(x,Q2) andxF3(x,Q2). Preliminary results from the next‐to‐leading order QCD analysis of deep inelastic charged current dimuon data are also shown. © 2004 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1664203

出版商:AIP    

年代:1904

数据来源: AIP

摘要:

The Fermilab E866/NuSea Collaboration has measured the Drell‐Yan dimuon cross sections in 800 GeV/c proton‐proton and proton‐deuterium collisions. This is the first measurement of the absolute Drell‐Yan cross section in proton‐proton collisions over a broad kinematic region and the most extensive study to date of the Drell‐Yan cross section in proton‐deuterium collisions. The Drell‐Yan mechanism is sensitive to both the beam and target parton distributions. In particular, with the kinematics of the E866/NuSea data, the Drell‐Yan mechanism is sensitive to the target antiquark distributions at low and intermediate Bjorken‐xand to the beam quark distributions at high‐x. Approximately 55K proton‐proton and 121K proton‐deuterium Drell‐Yan events over the longitudinal momentum fraction (Feynman‐x) range −0.05 <xF< 0.8 and the mass ranges 4.2 <M&mgr;+&mgr;−< 8.7 GeV and 10.85 <M< 16.85 GeV are included. The data analysis will be described, and the doubly‐differentialM3d2&sgr;/dMdxF, and triply‐differential cross sectionsEd3&sgr;/dp3will be presented. These results will be compared with previous measurements by E605 and E772 and to predictions based upon next‐to‐leading order calculations utilizing the MRST2001 and CTEQ6 global parton distribution function fits. The results indicate that recent global parton distribution fits provide a good description of the light antiquark sea in the nucleon over the Bjorken‐xrange 0.03 <x< 0.15. In contrast, the valence quark distributions appear to be overestimated by the current parton distribution fits asx→ 1; a region in which, prior to this data, there was very little proton data to constrain the global fits. © 2004 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1664204

出版商:AIP    

年代:1904

数据来源: AIP

摘要:

Results from QCD studies at the Tevatron from new Run 2 data are presented. The inclusive jet cross section and dijet mass spectrum are measured ats = 1960 GeVby the CDF and DO&slash; collaborations. CDF also reports results of searches for new particles decaying into dijets, and a study of jet shapes. © 2004 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1664205

出版商:AIP    

年代:1904

数据来源: AIP

摘要:

Results on soft and hard diffraction obtained by the CDF Collaboration at the Fermilab Tevatronp¯pCollider are reviewed with emphasis on aspects of the data that point to the underlying QCD mechanism for diffraction. The results are interpreted in terms of a phenomenological approach in which diffraction is due to an exchange of low‐xpartons subject to color constraints. © 2004 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1664206

出版商:AIP    

年代:1904

数据来源: AIP

摘要:

We have studied the production of fast neutrons and protons in proton positron collisions at the HERA collider. Results from experiments ZEUS and H1 are presented. Special detectors were used by the two experiments to detect particles emerging very close to the beam. The results support the assumption of vertex factorization. Measurements of theF2structure function was made as well as the pion structure functionF2&pgr;. Both of these structure functions behave as the electron protonF2structure function. © 2004 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1664207

出版商:AIP    

年代:1904

数据来源: AIP

摘要:

Exclusive coherent and incoherent electroproduction of the &rgr;0meson from1H and14N targets has been studied at the HERMES experiment as a function of coherence length (lc), corresponding to the lifetime of hadronic fluctuations of the virtual photon, and squared four‐momentum of the virtual photon (−Q2). The ratio of14N to1H cross sections per nucleon,callednuclear transparency, was found to increase (decrease) with increasing coherence length for coherent (incoherent) &rgr;0electroproduction. For fixed coherence length, a rise of nuclear transparency withQ2is observed for both coherent and incoherent &rgr;0production, which is in agreement with theoretical calculations of color transparency. © 2004 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1664208

出版商:AIP    

年代:1904

数据来源: AIP

摘要:

The HERMES experiment studies the spin structure of the nucleon using the 27.6 GeV longitudinally polarized positron beam of HERA and internal targets of pure gases. Recently, HERMES has published measurements of azimuthal single‐spin asymmetries in the hard electroproduction of photons on an unpolarized hydrogen target arising from the interference of the amplitudes of the Bethe‐Heitler (BH) and the Deeply Virtual Compton Scattering (DVCS) processes. The measurements constitute an effort towards accessing generalized parton distributions, and open a new approach to study the spin structure of the nucleon. © 2004 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1664209

出版商:AIP    

年代:1904

数据来源: AIP

摘要:

Generalized parton distributions provide a unifying framework for the interpretation of exclusive reactions at highQ2. The most promising reaction for the investigation of these distributions is the hard production of photons using Deeply Virtual Compton Scattering (DVCS). This reaction can be accessed experimentally by determining the production asymmetry using polarized electrons on a proton target. Pioneering experiments with CLAS and HERMES have produced the first measurements of this asymmetry. We will review the current experimental program to study DVCS at Jefferson Lab. Recent high statistics data taken with CLAS at 5.75 GeV allows us to determine this asymmetry at low −tin the valence region (xB=0.1–0.5) up to aQ2of 4 GeV2/c2. © 2004 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1664210

出版商:AIP    

年代:1904

数据来源: AIP

摘要:

The DIRAC experiment at CERN is presently measuring the lifetime of the pionium atom, a bound state of a &pgr;+and &pgr;−meson. The isospin 0 and 2 scattering length difference will be determined unambiguously once the value of the lifetime is known. In what follows we describe the present status of the experiment, the experimental goals and the first results. © 2004 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1664211

出版商:AIP    

年代:1904

数据来源: AIP