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VOLUME 113 | ISSUE 9 | PAGE 589
Understanding two slopes in the \boldsymbol{pp (p\bar p}) differential cross sections
Abstract
Recent experiments have discovered two exponents in the pp elastic differential cross sections with two different slope parameters, of the order (16-20) GeV-2 and (4-4.8) GeV-2 in the regions  -t \lesssim 0.5 GeV2 and -t \gtrsim 1 GeV2, respectively. We suggest a simple model of the pp elastic scattering with two types of particle exchanges: 1) when the exchanged particle transfers the momentum  Q from a quark of the proton p1 to one quark in another proton p2, producing the slope B1; 2) when the transfer occurs from two quarks in the p1 to two quarks in the p2, giving the exponent with the slope B2. The resulting amplitude is proportional to the product of the form factors of two protons, depending on  Q, but with different coefficients in the cases 1) and 2). Using the only parameter - the proton charge radius r2ch= 0.93 fm2, one obtains B1 = 16 GeV-2, B2 = 4 GeV-2 with the strict value of the ratio, \frac{B_1}{B_2} = 4.0, independent of rch. These predictions are surprisingly close to the data both in the pp and in the \bar p p differential cross sections. Comparison to experimental data and theoretical approaches is discussed, together with possible implications for the future development of the theory.