307 research outputs found
Hadron yields in Au+Au/Pb+Pb at RHIC and LHC from thermalized minijets
We calculate the yields of a variety of hadrons for RHIC and LHC energies
assuming thermodynamical equilibration of the produced minijets, and using as
input results from pQCD for the energy densities at midrapidity. In the
calculation of the production of partons and of transverse energy one has to
account for nuclear shadowing. By using two parametrizations for the gluon
shadowing one derives energy densities differing strongly in magnitude. In this
publication we link those perturbatively calculated energy densities of partons
via entropy conservation in an ideal fluid to the hadron multiplicities at
chemical freeze-out.Comment: 11 pages, 2 .eps figure
Distribution and density of α- and β-adrenergic receptor binding sites in the bovine mammary gland
Radioreceptor binding studies were designed to localize and determine the number of α and β-adrenergic receptors in the mammary gland of lactating cows. 3H-prazosin, 3H-rauwolscine and 3H-dihydroalprenolol were used for the regional characterization of α1, α2- and β-adrenergic receptors by competitive inhibition of binding of 3H-ligands with unlabelled adrenergic agonists and antagonists. The α1-, α2- and β2-adrenergic receptor subtypes could thus be demonstrated in the regions of the teats, large mammary ducts and parenchyma. Tissues of the teat wall, of the large mammary ducts above the gland cistern and of the mammary parenchyma were prepared to determine the density of α1, α2- and β-receptors by saturation binding assays using 3H-prazosin, 3H-rauwolscine and 3H-dihydroalprenolol respectively. Binding to high affinity sites was reversible within minutes and saturable. Equilibrium was reached within minutes. The number of α1-and α2-adrenergic receptors decreased from the teat to the mammary ducts to the parenchyma. Most of the α1- and α2-adrenergic receptors were found in the teat wall, whereas in the parenchyma α-adrenergic receptors were absent or barely detectable. The density of β-adrenergic receptors was similar in the teat wall and the large mammary ducts, but much lower in the parenchyma. Thus, α1, α2- and β-adrenergic receptors were found mainly in the milk purging system and hardly at all in mammary parenchyma. Inhibition of milk removal by α-adrenergic stimulation is possibly due to constriction of teat wall and to constriction of the mammary ducts, whereas enhanced milk flow after β-adrenergic stimulation is possibly due to relaxation not only of the teat sphincter and teat wall, but probably also of the large mammary duct
Distribution and density of α– and β–adrenergic receptor binding sites in the bovine mammary gland
Radioreceptor binding studies were designed to localize and determine the number of α and β-adrenergic receptors in the mammary gland of lactating cows. 3H-prazosin, 3H-rauwolscine and 3H-dihydroalprenolol were used for the regional characterization of α1, α2- and β-adrenergic receptors by competitive inhibition of binding of 3H-ligands with unlabelled adrenergic agonists and antagonists. The α1-, α2- and β2-adrenergic receptor subtypes could thus be demonstrated in the regions of the teats, large mammary ducts and parenchyma. Tissues of the teat wall, of the large mammary ducts above the gland cistern and of the mammary parenchyma were prepared to determine the density of α1, α2- and β-receptors by saturation binding assays using 3H-prazosin, 3H-rauwolscine and 3H-dihydroalprenolol respectively. Binding to high affinity sites was reversible within minutes and saturable. Equilibrium was reached within minutes. The number of α1-and α2-adrenergic receptors decreased from the teat to the mammary ducts to the parenchyma. Most of the α1- and α2-adrenergic receptors were found in the teat wall, whereas in the parenchyma α-adrenergic receptors were absent or barely detectable. The density of β-adrenergic receptors was similar in the teat wall and the large mammary ducts, but much lower in the parenchyma. Thus, α1, α2- and β-adrenergic receptors were found mainly in the milk purging system and hardly at all in mammary parenchyma. Inhibition of milk removal by α-adrenergic stimulation is possibly due to constriction of teat wall and to constriction of the mammary ducts, whereas enhanced milk flow after β-adrenergic stimulation is possibly due to relaxation not only of the teat sphincter and teat wall, but probably also of the large mammary ducts
Non-equilibrium initial conditions from pQCD for RHIC and LHC
We calculate the initial non-equilibrium conditions from perturbative QCD
(pQCD) within Glauber multiple scattering theory for AGeV and
ATeV. At the soon available collider energies one will
particularly test the small region of the parton distributions entering the
cross sections. Therefore shadowing effects, previously more or less
unimportant, will lead to new effects on variables such as particle
multiplicities , transverse energy production , and the
initial temperature . In this paper we will have a closer look on the
effects of shadowing by employing different parametrizations for the shadowing
effect for valence quarks, sea quarks and gluons. Since the cross sections at
midrapidity are dominated by processes involving gluons the amount of their
depletion is particularly important. We will therefore have a closer look on
the results for , , and by using two different
gluon shadowing ratios, differing strongly in size. As a matter of fact, the
calculated quantities differ significantly.Comment: typo in ref's removed, ack's added, no change in result
Charmonium suppression from purely geometrical effects
The extend to which geometrical effects contribute to the production and
suppression of the and minijet pairs in general is
investigated for high energy heavy ion collisions at SPS, RHIC and LHC
energies. For the energy range under investigation, the geometrical effects
referred to are shadowing and anti-shadowing, respectively. Due to those
effects, the parton distributions in nuclei deviate from the naive
extrapolation from the free nucleon result; . The strength
of the shadowing/anti-shadowing effect increases with the mass number. The
consequences of gluonic shadowing effects for the distribution of
's at GeV, GeV and TeV are
calculated for some relevant combinations of nuclei, as well as the
distribution of minijets at midrapidity for in the final state.Comment: corrected some typos, improved shadowing ratio
Single transverse-spin asymmetry in Drell-Yan lepton angular distribution
We calculate a single transverse-spin asymmetry for the Drell-Yan
lepton-pair's angular distribution in perturbative QCD. At leading order in the
strong coupling constant, the asymmetry is expressed in terms of a twist-3
quark-gluon correlation function T_F^{(V)}(x_1,x_2). In our calculation, the
same result was obtained in both light-cone and covariant gauge in QCD, while
keeping explicit electromagnetic current conservation for the virtual photon
that decays into the lepton pair. We also present a numerical estimate of the
asymmetry and compare the result to an existing other prediction.Comment: 15 pages, Revtex, 5 Postscript figures, uses aps.sty, epsfig.st
A microscopic calculation of secondary Drell-Yan production in heavy ion collisions
A study of secondary Drell-Yan production in nuclear collisions is presented
for SPS energies. In addition to the lepton pairs produced in the initial
collisions of the projectile and target nucleons, we consider the potentially
high dilepton yield from hard valence antiquarks in produced mesons and
antibaryons. We calculate the secondary Drell-Yan contributions taking the
collision spectrum of hadrons from the microscopic model URQMD. The
contributions from meson-baryon interactions, small in hadron-nucleus
interactions, are found to be substantial in nucleus-nucleus collisions at low
dilepton masses. Preresonance collisions of partons may further increase the
yields.Comment: 22 pages including 7 figures, submitted to Z. Phys.
Phenomenology of single spin asymmetries in p(transv. polarized)-p -> pion + X
A phenomenological description of single transverse spin effects in
hadron-hadron inclusive processes is proposed, assuming a generalized
factorization scheme and pQCD hard interactions. The transverse momentum, k_T,
of the quarks inside the hadrons and of the hadrons relatively to the
fragmenting quark, is taken into account in distribution and fragmentation
functions, and leads to possible non zero single spin asymmetries. The role of
k_T and spin dependent quark fragmentations -- the so-called Collins effect --
is investigated in details in p(transv. polarized)-p -> pion + X processes: it
is shown how the experimental data could be described, obtaining an explicit
expression for the spin asymmetry of a polarized fragmenting quark, on which
some comments are made. Predictions for other processes, possible further
applications and experimental tests are discussed.Comment: 20+1 pages, LaTeX, 6 eps figures, uses epsfig.sty. Version v2: Some
sentences rephrased and comments added throughout the paper; one reference
added; no changes in results and figures. Final version to be published in
Phys. Rev.
Single Spin Asymmetry in Lepton Angular Distribution of Drell-Yan Processes
We study the single spin asymmetry in the lepton angular distribution of
Drell-Yan processes in the frame work of collinear factorization. The asymmetry
has been studied in the past and different results have been obtained. In our
study we take an approach different than that used in the existing study. We
explicitly calculate the transverse-spin dependent part of the differential
cross-section with suitable parton states. Because the spin is transverse, one
has to take multi-parton states for the purpose. Our result agrees with one of
the existing results. A possible reason for the disagreement with others is
discussed.Comment: Typos corrected. Conclusions unchange
Null cone preserving maps, causal tensors and algebraic Rainich theory
A rank-n tensor on a Lorentzian manifold V whose contraction with n arbitrary
causal future directed vectors is non-negative is said to have the dominant
property. These tensors, up to sign, are called causal tensors, and we
determine their general properties in dimension N. We prove that rank-2 tensors
which map the null cone on itself are causal. It is known that, to any tensor A
on V there is a corresponding ``superenergy'' (s-e) tensor T{A} which always
has the dominant property. We prove that, conversely, any symmetric rank-2
tensor with the dominant property can be written in a canonical way as a sum of
N s-e tensors of simple forms. We show that the square of any rank-2 s-e tensor
is proportional to the metric if N<5, and that this holds for the s-e tensor of
any simple form for arbitrary N. Conversely, we prove that any symmetric rank-2
tensor T whose square is proportional to the metric must be, up to sign, the
s-e of a simple p-form, and that the trace of T determines the rank p of the
form. This generalises, both with respect to N and the rank p, the classical
algebraic Rainich conditions, which are necessary and sufficient conditions for
a metric to originate in some physical field, and has a geometric
interpretation: the set of s-e tensors of simple forms is precisely the set of
tensors which preserve the null cone and its time orientation. It also means
that all involutory Lorentz transformations (LT) can be represented as s-e
tensors of simple forms, and that any rank-2 s-e tensor is the sum of at most N
conformally involutory LT. Non-symmetric null cone preserving maps are shown to
have a causal symmetric part and are classified according to the null
eigenvectors of the skew-symmetric part. We thus obtain a complete
classification of all conformal LT and singular null cone preserving maps on V.Comment: 36 pages, no figures, LaTeX fil
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