共查询到20条相似文献,搜索用时 15 毫秒
1.
2.
3.
4.
It has been suggested that the pair annihilation of dark matter particles chi with mass between 0.5 and 20 MeV into e+e- pairs could be responsible for the excess flux (detected by the INTEGRAL satellite) of 511 keV photons coming from the central region of our Galaxy. The simplest way to achieve the required cross section while respecting existing constraints is to introduce a new vector boson U with mass M(U) below a few hundred MeV. We point out that over most of the allowed parameter space, the process e+e--->U(gamma), followed by the decay of U into either an e+e- pair or an invisible (nu(-)nu or chi(-)chi) channel, should lead to signals detectable by current B-factory experiments. A smaller, but still substantial, region of parameter space can also be probed at the Phi factory DAPhiNE. 相似文献
5.
《Physics letters. A》1987,120(8):407-412
Within a simple semiclassical model it is shown that the presence of an external Coulomb field induces only slight changes in the energy of a resonant electron-positron state unless for extremely small distances, while the width increases strongly with the field strength. 相似文献
6.
7.
《Physics letters. [Part B]》1988,207(3):273-277
The excitation function for Bhabha scattering was measured in the energy range between 760 and 840 keV (CM) in 1.4 keV steps with beams of monochromatic positrons scattered on a Be foil at angles between 79° and 101° (CM). The statistical accuracy was 0.5%. Up to an upper limit of 1.0 b eV/sr (CM) for the energy-integrated differential cross section (97% CL) no resonant scattering was observed. This limit corresponds to a maximal resonance contribution of 0.7% relatively to the Bhabha cross section, consistent with the upper bound, derived from precision measurements of the electron (g-2) factor. 相似文献
8.
9.
10.
11.
Arisaka K Auerbach LB Axelrod S Belz J Biery KA Buchholz P Chapman MD Cousins RD Diwan MV Eckhause M Ginkel JF Guss C Hancock AD Heinson AP Highland VL Hoffmann GW Horvath J Irwin GM Joyce D Kaarsberg T Kane JR Kenney CJ Kettell SH Kinnison WW Knibbe P Konigsberg J Kuang Y Lang K Lee DM Margulies J Mathiazhagan C McFarlane WK McKee RJ Melese P Milner EC Molzon WR Ouimette DA Riley PJ Ritchie JL Rubin P Sanders GH Schwartz AJ Sivertz M Slater WE Urheim J Vulcan WF Wagner DL Welsh RE Whyley RJ 《Physical review letters》1993,71(24):3910-3913
12.
13.
14.
There are many speculations that there exist quarks Q considerably heavier than the charmed quark. Their Q states will display a far richer spectrum of monochromatic photon and hadron transitions than charmonium. The most important features of this spectrum — in particular, its dependence on the mass of Q — are outlined. 相似文献
15.
Feldman GJ Abrams GS Amidei D Baden AR Barklow T Boyarski AM Boyer J Breidenbach M Burchat P Burke DL Butler F Dorfan JM Gidal G Gladney L Gold MS Goldhaber G Golding L Haggerty J Hanson G Hayes K Herrup D Hollebeek RJ Innes WR Jaros JA Juricic I Kadyk JA Karlen D Lankford AJ Larsen RR LeClaire BW Levi M Lockyer NS Lüth V Matteuzzi C Nelson ME Ong RA Perl ML Richter B Riles K Ross MC Rowson PC Schaad T Schellman H Schlatter D Schmidke WB Sheldon PD de la Vaissiere C Wood D Yelton JM Zaiser C 《Physical review letters》1985,54(21):2289-2291
16.
Ash WW Band HR Blume HT Camporesi T Chadwick GB Clearwater SH Coombes RW Delfino MC De Sangro R Fernandez E Ford WT Gettner MW Goderre GP Groom DE Heltsley BK Hurst RB Johnson JR Lau KH Lavine TL Lee HY Leedy RE Marini A Maruyama T Messner RL Moromisato JH Moss LJ Muller F Nelson HN Peruzzi I Piccolo M Prepost R Qi N Read AL Ritson DM Rosenberg LJ Shambroom WD Sleeman JC Smith JG Venuti JP von Goeler E Wald HB Weinstein R Wiser DE Zdarko RW 《Physical review letters》1985,54(23):2477-2480
17.
18.
Based on the picture of hadron cluster, some parameters about cluster are obtained in e+ e- annihilation and it is found that the intermittent behavior in e+ e- annihilation is closely related with short-range correlation from hadron cluster. 相似文献
19.