High-pt hadrons in the pionization region in QCD

Minijet production in hadronic and nuclear collisions through a BFKL pomeron ladder is studied for the energies of the future LHC heavy-ion collisions. We use unintegrated gluon densities compatible with the small-x increase of parton distributions observed at HERA. We show that at LHC energies the BFKL minijet and transverse energy production is at most of the same order of magnitude as that in the collinear factorization approach. CERN-TH/96-124 June 19961 On leave of absence from Laboratory of High Energy Physics, Department of Physics, University of Helsinki, Finland 2 Alexander von Humboldt Fellow, on leave from Lebedev Physics Institute, 117924 Leninski pr. 53, Moscow, Russia Semihard parton scatterings with transverse momenta p T ∼ few GeV have been suggested to explain the rapid growth of the inelastic and total cross sections in high energy pp(p) collisions at √ s > 20 GeV [1,2]. Especially in heavy-ion collisions at very high energies the semihard processes are expected to be abundant and dominate the transverse energy production in the central rapidity region [3]. Event generators emphasizing the importance of semihard processes in ultrarelativistic heavy-ion collisions at √ s ≥ 200 AGeV have also been actively developed during recent years [4,5].Perturbative processes take place at the very early stages of the time evolution of an ultrarelativistic heavy-ion collision [6]. In the central rapidity region, these semihard processes occur at time scales τ ∼ 1/p T , i.e. within the first fractions of fm/c, while the particle production from soft processes is expected to take longer, ∼ 1 fm/c. Therefore, semihard particle production and associated transverse energy production give initial conditions for further space-time evolution of the formed partonic system, which eventually may lead to a thermalized quark-gluon plasma if the produced system is dense enough. The key feature of the semihard parton production is that it can be computed by using perturbative QCD [3,6].At central rapidities the semihard scatterings with momentum exchanges p T ∼ 2 GeV probe typically parton distributions at x ∼ 2p T / √ s. Especially in nuclear collisions at the CERN Large Hadron Collider (LHC) with √ s = 5.5 TeV, these x-values fall dominantly in the region of a rapid increase of the structure function F p 2 (x, Q 2 ) as observed in deep inelastic ep collisions at HERA [7]. This increase persists down to Q 2 = 1.5 GeV 2 [8], thus strongly enhancing production of semihard partons as discussed in [9]. Nuclear effects in the parton distributions, in particular the observed nuclear shadowing of F A 2 (x, Q 2 ) at small x [10], are expected to be important, although the nuclear gluon distributions are not well known at the moment [11,12].In the above-mentioned studies, the production mechanism of semihard partons, minijets, is based on multiple independent 2 → 2 scatterings of partons. Collinear factorization is assumed to hold, enabling separation of the perturbatively calculable hard processes from the parton distribu...

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“…Then, the cross section for inclusive minijet production is bound to have the same structure as in Eq. (4), and one obtains [18,19] …”

Section: Cern-th/96-124 June 1996mentioning

confidence: 99%

“…Then, the cross section for inclusive minijet production is bound to have the same structure as in Eq. (4), and one obtains [18,19] where p T and y are the transverse momentum and the rapidity (in the hadron CMS) of the minijet. From momentum conservation and multi-Regge kinematics the momentum fractions become…”

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confidence: 99%

Minijet and transverse energy production in the BFKL regime

1996

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“…[8]. On the one hand, the set of equations obtained there leaves undetermined a regular function related to higher order contributions.…”

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confidence: 99%

“…In a second existing approach, explicit solutions have been proposed in a different context [8] . Using a constructive procedure starting directly from the structure functions, a system of evolution equations can be written following the scheme:…”

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confidence: 99%

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Unified QCD evolution equations and the dominant behaviour of structure functions at low x

Peschanski

Wallon

1995

Physics Letters B

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We consider a system of evolution equations for quark and gluon structure functions satisfying the leading-logarithmic behaviour due to both QCD collinear LLQ 2 and infrared (LL1/x) singularities. We show that these equations leave undetermined an arbitrary regular function of j in the Mellin-transformed weights. We consider the constraints resulting from energy-momentum conservation and from the decoupling of quark loops in the leading j-plane singularity. These constraints can be fulfilled without influencing the leading-log terms. As a particular consequence of the second constraint, the location of the leading singularity is determined in terms of the (LL1/x) and LLQ 2 kernels. It leads to a value significantly lower than the LL1/x evaluation, while remaining at j > 1, and compatible with the behaviour of structure functions observed at HERA.

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D⁰ meson production in high‐energy pp collisions based on dipole transverse momentum approach

2023

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By employing the color dipole approach in the momentum representation taking into account the nonlinear behavior of the QCD dynamics, we make predictions for the D‐meson differential cross‐section in terms of the transverse momentum and rapidity distributions considering pp collisions at the LHC. Moreover, a comparison between our results and the corresponding experimental measurements provided by the ALICE and LHCb experiments in different rapidity bins is performed.

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High-pt hadrons in the pionization region in QCD

Cited by 140 publications

References 4 publications

Minijet and transverse energy production in the BFKL regime

Minijet and transverse energy production in the BFKL regime

Unified QCD evolution equations and the dominant behaviour of structure functions at low x

D⁰ meson production in high‐energy pp collisions based on dipole transverse momentum approach

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High-pt hadrons in the pionization region in QCD

Cited by 140 publications

References 4 publications

Minijet and transverse energy production in the BFKL regime

Minijet and transverse energy production in the BFKL regime

Unified QCD evolution equations and the dominant behaviour of structure functions at low x

D0 meson production in high‐energy pp collisions based on dipole transverse momentum approach

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D⁰ meson production in high‐energy pp collisions based on dipole transverse momentum approach