e-A深度非彈性散射中膠子輻射振幅的新計(jì)算方法

1、30 5 2006 5HIGHENERGYPHYSICSANDNUCLEARPHYSICSVol. 30, No. 5May, 2006e-A *1;11;21( 430079e-A , , . e-A : QCD . , , .1e-A; e-A 4 , , QCD . . , ., , ( . , QCD , 4351,2,5e-A.2l q323 , , . , z g =1z 0( z g , z , , . , 1.2 . , , . , , . , QCD . : , ; ,5l q 0,l q , 0,l n l q q=0, 1, 0, .µ(p , p , . p

2、i =x i p +, 0, k T d x i /2,exp(i x i p +y i +i k T y i T , y i. , , :d x iµ(p 2e i x i p+y i +ik T ·y i T, (3418 (HEP &NP 30l T2(1z q , (1z q ,(4(l =T l TS2M ,(6yl2T c e i(x B +x L p+.(7T(xp +q l 2=2zp +q (x x B x L =0,(81z 0. , T c , c . , x B =Q 2/(2p +q Bjorken . , 3 :2x L =Tk 2T2p

3、 +q z, x D=M D(y,y 1 =2gT l TL 2, T(e(ci g e i x i p+y +i, (dg e i x i py i., 2(c,d x i p +k T , 2(b , , L , l .2 4L T(e : . . 3 , .5 e-A 419M (y,y 1 =2gaT l TM (y,y 1,y 2,y 3 =2i g 4bT l TM (y =2gST l TMDa(y,y 1 =2gT (l T (1z k T 420Db(HEP &NP 30M (y,y 1 =2gT l TM (y,y 1,y 2 =2gTfT (l T k T MDc

4、(y,y 1 =2gT (l T k T TgT l TM Ta(y,y T l T1,y 2 =2gMTb(y,y 1,y 2 =2gT (l T (1z k T MTc(y,y 1,y 2 =2gT l TMTd(y,y 1,y T (l T 2 =2gz k T M Te(y,y 1,y 2 =2gT (l T k T M (y,y 1,y 2 =2gH D=d 2l T1zd z M S (y +MD (y,y 1+MT (y,y 1,y 2, (245 e-A421M S, M T. , . QCD 5, . , .5. , . e-A 4 , , QCD . . , ,Gyulas

5、sy opacity 79, . , , opacity , . opacity , , , , ., ., 2(d , (, Pi P q qi µ(P q P q 2+i =2p +q (X X =all con +i i µ(P q µ(P 1q 2p +q ,µ(P qr (i gµi µ(P ql M , (6 (7, 2(a e i xp+y.2(c .Pi g g µ2p +l ,µ . , , 2(c , i g e i x i p+y i.2(b . , , 2(b . , (X all X co

6、n , 2(b . ,±X L , X L =L 2TT L TX L 2p +qµ=2g422 ( HEP & NP 30 (References 1 QIU Jian-Wei, Sterman G. Nucl. Phys., 1991, B353: 105 2 QIU Jian-Wei, Sterman G. Nucl. Phys., 1991, B353: 137 3 WANG X N, GUO X F. Nucl. Phys., 2001, A696: 788 4 GUO X F, WANG X N. Phys. Rev. Lett., 2000, 85:

7、3591 5 ZHANG Ben-Wei, WANG Xin-Nian. Nucl. Phys., 2003, A720: 429 6 LUO M, QIU J, Sterman G. Phys. Lett., 1992, B279: 377 7 Gyulassy M, L´vai P, Vitev I. Nucl. Phys., 2001, B594: e 371 8 Gyulassy M, L´vai P, Vitev I. Phys. Rev. Lett., 2000, 85: e 5535 9 WANG E, WANG X N. Phys. Rev. Lett.,

8、2001, 87: 142301 A New Calculational Approach to the Amplitude of Gluon Radiation in e-A DIS * GUO Yun1;1 WANG En-Ke1;2 1 (Institute of Particle Physics, Huazhong Normal University, Wuhan 430079, China Abstract In the deeply inelastic e-A scattering, the gluon radiation induced by multiple scatterin

9、g will lead to medium modication of the parton fragmentation functions and also associate with the energy loss of the leading quark. To obtain the hard partonic part of quark-gluon double scattering, one can do a complete calculation within the framework of generalized factorization in perturbative

10、QCD. In another way one can utilize the approach of helicity amplitude approximation(HAA to calculate the amplitude of gluon radiation. However, the two methods are both complicated and tedious. In this paper, we will introduce a new approach which enables one to calculate easily the amplitude for g

11、luon radiation in multiple scattering. The nal results obtained by using our new approach agree exactly with the complete calculation in perturbative QCD. Key words deeply inelastic scattering, amplitude for gluon radiation, modied fragmentation function, jet energy loss Received 9 October 2005 *Supported by National Natural Scie