Measurement of the diffractive cross section in deep inelastic scattering using ZEUS 1994 data

Abstract

The DIS diffractive cross section, d#sigma#_#gamma#_"*_p_#->#_X_N"d"i"f"f/dM_X, has been measured in the mass range M_X<15 GeV for #gamma#"*p c.m. energies 60 < W < 200 GeV and photon virtualities Q"2=7 to 140 GeV"2. For fixed Q"2 and M_X, the diffractive cross section rises rapidly with W, d#sigma#_#gamma#_"*_p_#->#_X_N"d"i"f"f(M_X,W,Q"2)/dM_X #propor to# W"a""d""i""f""f with a"d"i"f"f=0.507#+-#0.034(stat)_-_0_._0_4_6"+"0"."1"5"5(syst) corresponding to a t-averaged pomeron trajectory of /score#alpha#_P=1.127 #+-#0.009(stat)_-_0_._0_1_2"+"0"."0"3"9(syst) which is larger than anti #alpha#_P observed in hadron-hadron scattering. The W dependence of the diffractive cross section is found to be the same as that of the total cross section for scattering of virtual photons on protons. The data are consistent with the assumption that the diffractive structure function F_2"D"("3") factorizes according to x_PF_2"D"("3")(x_P,#beta#,Q"2)=(x_0/x_P)"nF_2"D"("2")(#beta#,Q"2). They are also consistent with QCD based models which incorporate factorization breaking. The rise of x_PF_2"D"("3") with decreasing x_P and the weak dependence of F_2"D"("2") on Q"2 suggest a substantial contribution from partonic interactions. (orig.)Available from TIB Hannover: RA 2999(98-084) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEDEGerman