Hadron mass corrections in semi-inclusive deep-inelastic scattering

Abstract

The spin-dependent cross sections for semi-inclusive lepton-nucleon scattering are derived in the framework of collinear factorization, including the effects of masses of the target and produced hadron at finite momentum transfer squared Q 2 . At leading order the cross sections factorize into products of parton distribution and fragmentation functions evaluated in terms of new, mass-dependent scaling variables. The size of the hadron mass corrections is estimated at kinematics relevant for future semi-inclusive deepinelastic scattering experiments.

Hadron Mass Effects on Kaon Multiplicities: HERMES vs. COMPASS

“…(2.1) for both experiments. frame, where p and q are collinear and have zero transverse momentum, one finds [13] …”

“…Assuming as usual that v 2 = 0 (which is a kinematically allowed value of k µ k µ , see Ref. [13,15]) one obtains z = ζ h and x = ξ 1 + v 2 Q 2 . On the other hand, the scattered parton is fragmenting into a massive hadron, and therefore needs a non vanishing virtuality v 2 .…”

“…These multiplicities have been measured by the HERMES [3,9] and COMPASS [10,11] collaborations showing large discrepancies between their measurements. However, these measurements are sensitive to relatively low values of photon virtualities (Q ≈ 1 − 4 GeV) where the mass m of the target nucleon and the mass m h of the observed hadron, in this case the Kaon (m K ≈ 0.5 GeV), induce non-negligible "Hadron Mass Corrections" (HMCs) of order O(m 2 /Q 2 ) [12,13].…”

Gauge invariance and kaon production in deep inelastic scattering at low scales

“…[22,23]; this is recalled in Sec. II, where we pay special attention to the conceptual underpinnings of the formalism and to explicitly discuss the gauge invariance of the mass-corrected SIDIS cross section, that has been criticized in Ref.…”

“…These have been measured on deuteron targets by the HERMES [14,19] and COMPASS [20,21] collaborations, that however show large discrepancies in their results. These measurements are sensitive to relatively low values of photon virtualities Q 2 , where the mass of the target and observed hadron, generically denoted by m, induce "hadron mass corrections" (HMCs) of order Oðm 2 =Q 2 Þ that can be larger than the experimental uncertainties [22,23]. Crucially, with a kaon mass m K ≈ 0.5 GeV and scales Q ≈ 1-4 GeV, hadron mass corrections may be non negligible even at relatively high energy experiments such as HERMES and COMPASS.…”