Predictions forD*±photoproduction at DESY HERA with new fragmentation functions from CERN LEP 1

Abstract

We present new sets of nonperturbative fragmentation functions for D* Ϯ mesons, both at leading and next-to-leading order in the MS factorization scheme with five massless quark flavors. They are determined by fitting the latest OPAL and ALEPH data on inclusive D* Ϯ production in e ϩ e Ϫ annihilation. We take the charm-quark fragmentation function to be of the form proposed by Peterson et al. and thus obtain new values of the ⑀ c parameter, which are specific for our choice of factorization scheme. With these fragmentation functions, recent data on inclusive D* Ϯ photoproduction in ep collisions at DESY HERA are reasonably well reproduced.

Fragmentation fractions of $$c$$ c and $$b$$ b quarks into charmed hadrons at LEP

“…However, to describe completely the heavy quark transition into a given hadron, a non-perturbative parametrisation tuned to experimental results is needed. Fragmentation functions, used to parametrise a transfer of quark's energy to a given hadron, are expected to be rather different for different pQCD calculations [1][2][3]. Fragmentation fractions are probabilities for c/b quark to hadronise as a particular charmed/bottom hadron, f (c → H c )/ f (b → H b ).…”

Optical spectroscopy of trapped neutral atoms

“…With such improvement large statistic samples with high E T jets will allow more precise QCD tests. The measurement o f high p T inclusive c harged particle spectra has been recently proposed as a valid alternative to have access to the parton distributions in the photon [99]. It has the advantage of being insensitive to the energy scale of the calorimeter, at the price of an uncertainty due to the fragmentation functions, needed to describe the transition from partons to hadrons.…”

“…The high p T inclusive particle cross section has recently been considered an important tool to extract precise parton distributions in the photon in the poorly known regions of x > 0:8 and x < 0:05 [99]. It has the advantage of being insensitive to possible multiple interactions or soft underlying event eects, discussed in section 7.3, as opposed to jet measurements.…”

Colour-octet contributions to photoproduction via fragmentation at HERA

“…At NLO, the direct-and resolved-photon contributions both strongly depend on the factorization scheme and scale, and must be combined in order to give a well-defined physical observable. From previous experience in connection with inclusive pion, kaon [15], and D * ± [16,17] photoproduction at HERA, one may infer that, in the case of J/ψ photoproduction via fragmentation, the resolved-photon contribution, which was disregarded in Ref. [14], is likely to be much more important than the direct one.…”

“…The evolution of D i→H (x, µ 0 ) up to higher fragmentation scales µ is ruled by the timelike Altarelli-Parisi equations, which may be conveniently solved at NLO in x space [17].…”