Particle reaction at HERA

我们研究了1992年4月在汉堡在DESY的世界第一电子质子对撞机HERA的粒子反应。Search for the scalar top quark（stop）（1） Stop production in the min？supersymmetric model（MSSM） ：We investigated the light scalar top quark via boson-gluon fusion at HERA， based on the MSSM ; e\@D1 *@> D1p*e\@D4-@>D4\@> D21@>D2t\@D4\@> D21\@D4 @> D4@>D2X。“计算结果已经从两个精确的树层次和Weizsacker-Williams近似值中提取出来。It has been shown that the total cross section is larger than 0. 1 pb if the mass of the stop m<@D2t <@D4·@>D4<@D21 @>D2@>D2， （] SY. ltorsim。[） 50 GeV和光子-gluon对子过程的贡献远远大于Z-boson-gluon。Since the former does not depend upon the stop mixing angle theta<@D2t @> D2， the cross section is not sensitive to theta<@D2t @>D2， but only depends upon the stop mass m<@D2t <@D4·@>D4<@D21 @> D2@>D2。这使我们能够搜索一个可能的参数区域 ... More ters for the existence of light scalar top quark at HERA in a wider parameter space （m\@D2t\@D4-@>D4@>D2，theta\@D2t @>D2） than LEP。（2）R-奇偶破坏模型（RPBM）中的停止共振：在RBM中可能存在由（-1）定义的R-奇偶校验异常的Yukawa偶联，其中R-奇偶校验偶联被破坏^<3B+L+2S>、L、B和S构成瘦骨嶙峋的数、巴里昂数和自旋，尊重。这是电子夸克子处理中的S-通道共振， e^*p*（t^^-_1X）*e^*d^<（-）>X。一个清晰的峰值可能会预期在Bjorken参数分布作为这个过程的一个清晰的信号。我们可以将HERA的潜力归结为，以发现停止的共振，或通过详细分析的包容性中性当前过程的详细分析来产生非常严重的上行边界。Radiative corrections to deep inelastic electron-proton scattering at HERAWe have calculated one-loop electromagnetic radiative corrections delta_<NC>to neutral current deep inelastic electron-proton scattering.我们发现：（1）delta_<NC>确实是光子的切断能量的独立性， （2）delta_<NC>也是夸克-粒子分布函数的最佳选择。Less（低）

We have studied particle reactions realized at the world first electron-proton collider HERA in DESY,Hamburg in April 1992.1. Search for the scalar top quark(stop)(1) Stop production in the minimal supersymmetric model(MSSM) :We investigated the light scalar top quark via boson-gluon fusion at HERA, based on the MSSM ; e<@D1*@>D1p*e<@D1*@>D1t<@D4-@>D4<@D21@>D2t<@D4-@>D4<@D21<@D4・@>D4@>D2X. The calculations have been carried out both an exact tree level and the Weizsacker-Williams approximation. It has been shown that the total cross section is larger than 0.1 pb if the mass of the stop m<@D2t<@D4・@>D4<@D21@>D2@>D2, (] SY.ltorsim.[) 50 GeV and that the photon-gluon contribution to the subprocess is much larger than that of the Z boson-gluon. Since the former does not depend upon the stop mixing angle theta<@D2t@>D2, the cross section is not sensitive to theta<@D2t@>D2, but only depends upon the stop mass m<@D2t<@D4・@>D4<@D21@>D2@>D2. This enables us to search a possible region of parame … More ters for the existence of light scalar top quark at HERA in a wider parameter space (m<@D2t<@D4-@>D4@>D2,theta<@D2t@>D2) than LEP.(2) Stop resonances in R-parity breaking model(RPBM) :In the RBM there could exist the exotic Yukawa couplings of the stop t^^-_1 which violate the R-parity defined by (-1)^<3B+L+2S>, L, B and S being the lepton number, baryon number and spin, respectively. This induces the s-channel resonances in the electron-quark subprocesses, e^*p*(t^^-_1X)*e^*d^^<(-)>X. A sharp peak could be expected in the Bjorken parameter distribution as a clear signal for this process. We can conclude that HERA has a potential ability to discover the stop resonances or to impose a very severe upper bound for the R-parity breaking coupling through the detailed analyses of inclusive neutral current processes.2. Radiative corrections to deep inelastic electron-proton scattering at HERAWe have calculated one-loop electromagnetic radiative corrections delta_<NC> to neutral current deep inelastic electron-proton scattering. We found that (1) delta_<NC> is really independent of the cut-off energy of the photon, (2) delta_<NC> is almost independent of the choice of the quark-parton distribution functions. Less