16 research outputs found
Exclusive meson pair production in peripheral ultrarelativistic heavy ion collisions
The cross sections for exclusive and meson pair
production in peripheral nucleus - nucleus collisions are calculated and
several differential distributions are presented. The calculation of the
elementary cross section is done within the
heavy-quark approximation and in the Brodsky- Lapage formalism with
distribution amplitudes describing recent CLEO data on leptonic decay.
Realistic (Fourier transform of charge density) charge form factors of nuclei
are used to generate photon flux factors. Absorption effects are discussed and
quantified. The cross sections of a few nb are predicted for RHIC and of a few
hundreds of nb for LHC with details depending on the approximation made in
calculating elementary cross sections.Comment: 11 pages, 8 figure
Exclusive Four-pion Photoproduction in Ultra-peripheral Heavy-ion Collisions at RHIC and LHC Energies
We study the photoproduction of exclusive 2π+2π− mesons in ultra-peripheral heavy-ion collisions at the RHIC and LHC energies. Predictions in photon–nucleus interactions are calculated for various resonances at central and forward rapidities. The recent H1 preliminary data are utilized to improve the description of the poorly known γp→4π±p process. We present the comparisons of our results to the available STAR data at RHIC, and made predictions for the LHC energies
Exclusive production of large invariant mass pion pairs in ultraperipheral ultrarelativistic heavy ion collisions
The cross section for exclusive production of and
meson pairs in ultrarelativistic heavy ion collisions is calculated for LHC
energy 3.5 TeV taking into account photon-photon mechanism.
We concentrate on the production of large two-pion invariant masses where the
mechanism of the elementary process is not fully
understood. In order to include a size of nuclei we perform calculation in the
impact-parameter equivalent photon approximation (EPA). Realistic charge
densities are used to calculate charged form factor of Pb nucleus and
to generate photon fluxes associated with ultrarelativistic heavy ions.
Sizeable cross sections are obtained that can be measured at LHC. The cross
section for elementary is calculated in the
framework of pQCD Brodsky-Lepage (BL) mechanism with the distribution amplitude
used to descibe recent data of the BABAR collaboration on pion transition form
factor, using hand-bag mechanism advocated to describe recent Belle data as
well as and -channel meson/reggeon exchanges. We present distributions
in two-pion invariant mass as well as the pion pair rapidity for the nuclear
process.Comment: 13 pages, 10 figure
Exclusive production of and pairs in photon-photon and in ultrarelativistic heavy ion collisions
The reactions are discussed. To describe those
processes, we include dipion continuum, resonances, high-energy pion-pion
rescatterings, meson exchange and pQCD Brodsky-Lepage mechanisms. The
cross section for the production of pion pairs in photon-photon collisions in
peripheral heavy ion collisions is calculated with the help of Equivalent
Photon Approximaption (EPA) in the impact parameter space. We show predictions
at TeV which could be measured e.g. by the ALICE
collaboration at the LHC.Comment: 4 pages, 7 figures, 1 table, talk by M. Klusek-Gawenda at MESON2012,
31 May - 5 June 2012, Krakow, Polan
The reaction and the pair production in exclusive ultraperipheral ultrarelativistic heavy ion collisions
We calculate the cross section for the
process. Two mechanisms are considered: box (two-loop) diagrams of the order of
and two-gluon exchange of the order of
. The first mechanism is calculated in the
heavy-quark non-relativistic approximation while the second case we also
include the effects of quantum motion of quarks in the bound state. The box
contribution dominates at energies close to the threshold ( 15 GeV) while
the two-gluon mechanism takes over at 15 GeV. Including the bound-state
wave function effects for the two-gluon exchange mechanism gives a cross
section 0.1 - 0.4 pb, substantially smaller than that in the non-relativistic
limit (0.4 - 1.6 pb). We also find a strong infrared sensitivity which
manifests itself in a rather strong dependence on the mass for the -channel
gluons. The elementary cross section is then used in the Equivalent Photon
Approximation (EPA) in the impact parameter space to calculate the cross
section for
reaction. Distributions in rapidity of the pair and invariant
mass of the pair are shown.Comment: 15 pages, 11 figure
Ultraperipheral production of very small number of particles in ultrarelativistic heavy ion collisions *
We review our recent results on exclusive production of μ+μ−, heavy quark - antiquark and meson-antimeson pairs in ultraperipheral, ultrarelativistic heavy ion collisions
Exclusive electromagnetic production of pion pairs in lead-lead collisions at LHC
The cross section for π+π− and π0π0 meson pairs production in peripheral ultrarelativistic heavy-ion collisions is calculated in the impact parameter space equivalent photon approximation. The cross section is calculated at the energy available at the CERN Large Hadron Collider, √sNN = 3.5 TeV. For the first time the world data for γγ → ππ are described, both for the total cross section and for the angular distribution. This is obtained simultaneously for γγ → π+π− and γγ → π0π0 at all experimentally available energies
Diphoton production in lead-lead and proton-proton UPC
We discuss diphoton semi(exclusive) production in ultraperipheral P bP b collisions at energy of √ sNN = 5.5 TeV (LHC). The nuclear calculations are based on equivalent photon approximation in the impact parameter space. The cross sections for elementary γγ → γγ subprocess are calculated including three different mechanisms: box diagrams with leptons and quarks in the loops, a VDM-Regge contribution with virtual intermediate hadronic excitations of the photons and the two-gluon exchange contribution (formally three-loops) to elastic photon-photon scattering in the high-energy approximation. We got relatively high cross sections in P bP b collisions (306 nb). This opens a possibility to study the γγ → γγ (quasi)elastic scattering at the LHC. We find that the cross section for elastic γγ scattering could be measured in the lead-lead collisions for the diphoton invariant mass up to Wγγ ≈ 15 − 20 GeV. We identify region(s) of phase space where the twogluon exchange contribution becomes important ingredient compared to box and nonperturbative VDM-Regge mechanisms. We perform a similar analysis for the pp → ppγγ reaction at energy of √ sNN = 7 and 100 TeV
Studying the interplay of strong and electromagnetic forces in heavy-ion collisions with NICA
In the following we stress the advantages of the NICA research programme in the context of studying the spectator-induced electromagnetic phenomena present in heavy-ion collisions. We point at the specific interest of using these phenomena as a new, independent source of information on the space-time evolution of the reaction and of the non-perturbative process of particle production. We propose an extended series of measurements of well-defined observables to be performed in different types of nuclear reactions and in the whole range of collision energies available to NICA. We expect these measurements to bring very valuable new insight into the mechanism of non-perturbative strong interactions, complementary to the studies made at the SPS at CERN, RHIC at BNL, and the LHC