Recently there are several evidences of the increase of the total cross section sigma(tot) to be log2 s consistent with the Froissart unitarity bound, and the COMPETE collaborations in the PDG have further assumed sigma(tot) = B log2(s/s0) to extend its universal rise with a common value of B for all the hadronic scatterings. However, there is no rigorous proof yet based only on QCD. Therefore, it is worthwhile to prove this universal rise of sigma(tot) even empirically. In this letter we attempt to obtain the value of B for pi p scattering, B(pi p), with reasonable accuracy by taking into account the rich pi p data in all the energy regions. We use the finite-energy sum rule(FESR) expressed in terms of the pi p scattering data in the low and intermediate energies as a constraint between high-energy parameters. We then have searched for the simultaneous best fit to the sigma(tot) and rho ratios, the ratios of the real to imaginary parts of the forward scattering amplitudes. The lower energy data are included in the integral of FESR, the more precisely determined is the non-leading term such as log s, and then helps to determine the leading terms like log2 s. We have derived the value of B(pi p) as B(pi p)=0.311 +- 0.044mb. This value is to be compared with the value of B for pbarp,pp scattering, B(pp), in our previous analysis[11], B(pp)=0.289 +- 0.023mb. Thus, our result appears to support the universality hypothesis.
We assume that the Pomeron is a sum of Regge multipoles, each corresponding to a finite gluon ladder. From a fit to the diffraction cone data of pp- and pbarp- scattering we found that the triple pole is significant for the rise of the ratio sigma_el/sigma_tot at high energies.
We describe a QCD motivated model for total cross-sections which uses the eikonal representation and incorporates QCD mini-jets to drive the rise with energy of the cross-section, while the impact parameter distribution is obtained through the Fourier transform of the transverse momentum distribution of soft gluons emitted in the parton-parton interactions giving rise to mini-jets in the final state. A singular but integral expression for the running coupling constant in the infrared region is part of this model.
A previously successful model for purely hadronic total cross-sections, based on QCD minijets and soft-gluon resummation, is here applied to the total photoproduction cross section. We find that our model in the gamma p case predicts a rise with energy stronger than in the pp -pbarp case.
As noticed by Fadin, Kuraev and Lipatov in 1975 incorporation of asymptotic freedom into the BFKL equation splits the QCD pomeron into a series of isolated poles in complex angular momentum plane. Following our earlier work on the proton structure function we explore the phenomenological consequences of the emerging BFKL-Regge factorized expansion for the small-$x$ structure function of the pion $F_{2π}(x,Q^2)$. We calculate $F_{2π}$ in a small-$x$ region and find good agreement with the recent H1 determination of $F_{2π}(x,Q^2)$. We also present the BFKL-Regge factorization based evaluation o…
Saturation of the Froissart-Martin unitarity bound that the total cross sections increase like log2(s/s_0) appears to be confirmed. Due to this statement, the B log2(s/s_0) was assumed to extend the universal rise of all the total hadronic cross sections to reduce the number of adjustable parameters by the COMPETE Collaboration in the Particle Data Group (2006). Based on this assumption of parametrization, we test if the assumption on the universality of $B$ is justified through investigations of the value of B for pi p(K p)$ and pbar p, pp scatterings. We search for the simultaneous best fit …
An impact parameter representation for soft gluon radiation is applied to obtain both the initial decrease of the total cross-section ($σ_{tot}$) for proton-proton collisions as well as the later rise of $σ_{tot}$ with energy for both $pp$ and $p\bar{p}$. The non-perturbative soft part of the eikonal includes only limited low energy gluon emission and leads to the initial decrease in the proton-proton cross- section. On the other hand, the rapid rise in the hard, perturbative jet part of the eikonal is tamed into the experimentally observed mild increase by soft gluon radiation whose maximum e…
Recently there are several evidences of the hadronic total cross section sigma(tot) to be proportional to B (log s)2 consistent with the Froissart unitarity bound. The COMPETE collaborations have further assumed sigma(tot) = B (log s/s0)2 + Z to extend its universal rise with the common value of B and s0 for all hadronic scatterings to reduce the number of adjustable parameters. The coefficient B was suggested to be universal in the arguments of colour glass condensate (CGC) of QCD in recent years. There has been, however, no rigorous proof yet based only on QCD. We attempt to investigate the …
In this note we address the issue of theoretical estimates of the hadronic cross-sections for \gamgam processes. We compare the predictions of the minijet model with data as well as other models, highlighting the band of uncertainties in the theoretical predictions as well as those in the final values of the $σ(\gamgam \go {\rm hadrons})$ extracted from the data. We find that the rise of $σ_{γγ}^{\rm tot}$ with energy shown in the latest \gamgam data is in tune with the faster rise expected in the Eikonal Minijet Models (EMM). We present an estimate of the accuracy with which this cross-sectio…
The LHC measurements above SPS and Tevatron energies give the opportunity to test predictions of non-extensive thermodynamical picture of hadronic interaction to examine measured transverse momenta distributions for new interaction energy range. We determined Tsallis model non-extensivity parameter for the hadronization process before short-lived particles decayed and distort the initial p_t distribution. We have shown that it follows exactly smooth rise determined at lower energies below present LHC record. The shape of the q parameter energy dependence is consistent with expectations and the…
We compare the high energy behaviour of hadronic photon-photon cross-sections in different models. We find that the photon-photon cross-section appears to rise faster than the purely hadronic ones (proton-proton and proton-antiproton).
The drag and diffusion coefficients of a hot hadronic medium have been evaluated by using hidden charm mesons as probes. The matrix elements for the evaluation of these coefficients are calculated using an effective theory as well as from scattering lengths. Although the transport coefficients show a significant rise with temperature its effects on the suppression of $J/ψ$ in hadronic matter is not significant.
Demanding the analyticity of hadronic observables (calculated in terms of power series of the running coupling) as a {\it whole}, we show that they are free of the Landau singularity. Employing resummation and dispersion-relation techniques, we compute in a unifying way power corrections to two different hard-scattering functions in perturbative QCD: the electromagnetic pion form factor to leading order and the inclusive cross section of the Drell-Yan process. In the second case, the leading nonperturbative power correction in $bΛ_{\rm QCD}$ gives rise to a Sudakov-like exponential factor in t…
It is shown that the fusion of strings is a source of particle production in nucleus--nucleus collisions outside the kinematical limits of nucleon--nucleon collisions. The spectrum of different particles is compared with the high energy data on p--A collisions obtaining a reasonable agreement. Results for A--B collisions at $\sqrt{s}=19.4$ AGeV and $\sqrt{s}=200$ AGeV are given. It is shown that the fusion of strings can accelerate particles up to the highest energy detected in cosmic rays without help of any additional cosmic accelerator. Also the rise of the average shower depth of maximun f…
In the present review we discuss different aspects of the two-photon exchange (TPE) physics in elastic $ep$ scattering, at high $Q^2$ as well as at low $Q^2$. The imaginary part of the TPE amplitude gives rise to beam and target single-spin asymmetries. Different theoretical approaches to calculation of these observables are considered. The real part of the TPE amplitude influence unpolarized cross section and double-spin observables and is, most likely, responsible for discrepancy between two methods of proton form factors measurements. We review different methods of calculations of the TPE a…
The dependence of the one dimensional Bose-Einstein correlation R_1D derived from proton-proton collisions is examined in terms of energy, hadron multiplicity and number of emerging hadronic jets. It is argued that the observed rise of R_1D with energy is the result of the increase of the average number of hadronic jets. It is further shown that by the relative straightforward measurements of R_1D and its chaoticity parameter $λ$ one should be able to estimate the average number of outgoing hadronic jets emitted over the entire final state phase space without the necessity to rely on a particu…
Momenta of charmonia created in Pb-Pb collisions at the Large Hadron Collider are so large that three or more mesons may be produced when the charmonia collide with light mesons in hadronic matter. We study the meson-charmonium collision in a mechanism where the collision produces two quarks and two antiquarks, the charm quark then fragmenting into charmed mesons, and the other three constituents as well as quarks and antiquarks created from vacuum give rise to two or more mesons. The absolute square of the transition amplitude for the production of two quarks and two antiquarks is derived fro…
The azimuthal anisotropies of the collective transverse flow of hadrons are investigated in a large range of heavy-ion collision energy within the Parton-Hadron-String Dynamics (PHSD) microscopic transport approach which incorporates explicit partonic degrees of freedom in terms of strongly interacting quasiparticles (quarks and gluons) in line with an equation-of-state from lattice QCD as well as dynamical hadronization and hadronic dynamics in the final reaction phase. The experimentally observed increase of the elliptic flow $v_2$ with bombarding energy is successfully described in terms of…
The status of some popular models to simulate hadronic and nuclear interactions at Cosmic Ray energies is reviewed. The models predict the rise of all the hadronic and nuclear cross sections with energy and a smooth (logarithmic) rise of average multiplicities, rapidity plateaus and average transverse momenta with the energy. The importance is stressed to put more effort into the models and especially a better understanding of the minijet component at the highest energies. Likewise, experimental data on particle production are needed at the highest possible energies, to guide the models.
We apply the dipole formalism that has been developed to describe low-x deep inelastic scattering to the case of ultra-high energy real photons with nucleon and nuclear targets. We hope that there will be future modeling applications in high-energy particle astrophysics. We modify the dipole model of McDermott, Frankfurt, Guzey, and Strikman (MFGS) by fixing the cross section at the maximum value allowed by the unitarity constraint whenever the dipole model would otherwise predict a unitarity violation. We observe that, under reasonable assumptions, a significant fraction of the real photon cr…
A forward amplitude analysis on $pp$ and $\bar{p}p$ elastic scattering above 5 GeV is presented. The dataset includes the recent high-precision TOTEM measurements of the $pp$ total and elastic (integrated) cross-sections at 7 TeV and 8 TeV. Following previous works, the leading high-energy contribution for the total cross-section ($σ_{tot}$) is parametrized as $\ln^γ(s/s_h)$, where $γ$ and $s_h$ are free \textit{real} fit parameters. Singly-subtracted derivative dispersion relations are used to connect $σ_{tot}$ and the rho parameter ($ρ$) in an analytical way. Different fit procedures are con…
Bjorken scaling violation in deep inelastic electron-proton scattering (DIS) is related to the rise of hadronic cross sections by using the additive quark model. Of special interest is the connection between saturation in the low-$x$ behavior of the DIS structure functions (SF) and possible slow-down of the $pp$ cross section rise due to saturation effects. We also identify saturation effects in the DIS SF with phase transition that can be described by the Van der Waals equation of state.
The increase of the measured hadronic total cross sections at the highest energies is empirically described by squared log of center-of-mass energy sqrt s as sigma(tot)= B (log s)2, consistent with the energy dependence of the Froissart unitarity bound. The coefficient B is argued to have a universal value, but this is not proved directly from QCD. In the previous tests of this universality, the p(pbar)p, pi p, and K p forward scatterings were analyzed independently and found to be consistent with B(pp) = B(pip) = B(Kp), although the determined value of B(Kp) had large uncertainty. In the pres…
We discuss a model for total hadronic and photonic cross-sections which includes hard parton-parton scattering to drive the rise and soft gluon resummation to tame it. Unitarity is ensured by embedding the cross-section in the eikonal formalism. Predictions for LHC and ILC are presented.
Previous extensive studies on the dependence of the average transverse momentum, its slope as a function of the hadron mass and the average transverse expansion on the particle multiplicity per unit rapidity and unit transverse overlap area of the colliding partners are extended to the ratio of the energy density to the entropy density. The behaviour of the ratio between the average transverse momentum and the square root of the particle multiplicity per unit rapidity and unit transverse overlap area $\langle p_T \rangle/\sqrt{\langle dN/dy\rangle/S_{\perp}}$ as a function of collision energy …
We demonstrate the existence of an anomalous structure in the data on the diffractive elastic scattering of hadrons at high energies and small momentum transfer. We analyze five sets of experimental data on $p(\overline{p})-p $ scattering from five different experiments with colliding beams, ranging from the first-- and second--generation experiments at $\sqrt{s} = 53 $ GeV to the most recent experiments at 546 GeV and at 1800 GeV. All of the data sets exhibit a localized anomalous structure in momentum transfer. We represent the anomalous behavior by a phenomenological formula. This is based …
The rise of the total, elastic and inelastic hadronic cross sections at high energies is investigated by means of an analytical parametrization, with the exponent of the leading logarithm contribution as a free fit parameter. Using derivative dispersion relations with one subtraction, two different fits to proton-proton and antiproton-proton total cross section and rho parameter data are developed, reproducing well the experimental information in the energy region 5 GeV - 7 TeV. The parametrization for the total cross sections is then extended to fit the elastic (integrated) cross section data…
We analyze multiparticle production in a thermal framework for 7 central nucleus nucleus collisions, $e^+$+ $e^-$ annihilation into hadrons on the Z resonance and 4 hadronic reactions (p+p and p+$\bar{p}$ with partial centrality selec tion), with center of mass energies ranging from $\sqrt{s}$= 2.6 GeV (per nucleon pair) to 1.8 TeV. Thermodynamic parameters at chemical freeze-out (temperature and baryon and strangeness fugacities) are obtained from appropriate fits, generally improving in quality for reactions subjected to centrality cuts. All systems with nonvanishing fugacities are extrapola…
The energy dependence of the total hadronic cross section at high energies is investigated with focus on the recent experimental result by the TOTEM Collaboration at 7 TeV and the Froissart-Martin bound. On the basis of a class of analytical parametrization with the exponent $γ$ in the leading logarithm contribution as a free parameter, different variants of fits to $pp$ and $\bar{p}p$ total cross section data above 5 GeV are developed. Two ensembles are considered, the first comprising data up to 1.8 TeV, the second also including the data collected at 7 TeV. We shown that in all fit variants…
Within a QCD-based eikonal model with a dynamical infrared gluon mass scale we discuss how the small $x$ behavior of the gluon distribution function at moderate $Q^{2}$ is directly related to the rise of total hadronic cross sections. In this model the rise of total cross sections is driven by gluon-gluon semihard scattering processes, where the behavior of the small $x$ gluon distribution function exhibits the power law $xg(x,Q^2)= h(Q^2)x^{-ε}$. Assuming that the $Q^{2}$ scale is proportional to the dynamical gluon mass one, we show that the values of $h(Q^2)$ obtained in this model are comp…
The phenomenon of beamstrahlung can give rise to potentially dangerous hadronic backgrounds due to minjet production at the future linear colliders as well as at the γγcolliders that are under consideration. In this talk I will review briefly the current estimates of these backgrounds and predictions of the eikonalised minijet model for \siginel. I end by pointing out issues that need to be studied in more detail to firm up our estimates of these backgrounds.
In this talk I present the results of an analysis of total and inelastic hadronic cross-sections for photon induced processes in the framework of an eikonalised minijet model(EMM). We fix the various input parameters to the EMM calculations by using the data on photoproduction cross-sections and then make predictions for $\siggmhad$ using same values of the parameters. We then compare our predictions with the recent measurements of $\siggmhad$ from LEP. We also show that in the framework of the EMM the rise with $\rts$ of the total/inelastic cross-sections will be faster for photon induced pro…
We develop a dipole model for HERA DIS data which incorporates the impact parameter distribution of the proton. The model describes the inclusive total $γ^*p$ cross-sections as well as the diffractive $J/ψ$ differential cross-sections. We compare the model with previous approaches and show that the $t$-distributions are sensitive to saturation phenomena. We estimate the boundary of the saturation region and show that it dominates the data in the low-$Q^2$ region where the total $γ^*p$ cross-section exhibits the same universal rise as hadronic cross-sections. The model is then extended to nucle…
Recent results for the total and inelastic hadronic cross-sections from LHC experiments are compared with predictions from a single channel PDF driven eikonal mini-jet model and from an empirical model. The role of soft gluon resummation in the infrared region in taming the rise of mini-jets and their contribution to the increase of the total cross-sections at high energies are discussed. Survival probabilities at LHC, whose theoretical estimates range from circa 10 percent to a few per mille, will be estimated in this model and compared with results from QCD inspired models and from multi cha…
The gauge-links connecting the parton field operators in the hadronic matrix elements appearing in the transverse momentum dependent distribution functions give rise to T-odd effects. Due to the process-dependence of the gauge-links the T-odd distribution functions appear with different pre-factors. A consequence is that in the description of single spin asymmetries the parton distribution and fragmentation functions are convoluted with gluonic pole cross sections rather than the basic partonic cross sections. In this paper we calculate the gluonic pole cross sections encountered in single spi…
We discuss recent observations of high energy cosmic ray positrons and electrons in the context of hadronic interactions in supernova remnants, the suspected accelerators of galactic cosmic rays. Diffusive shock acceleration can harden the energy spectrum of secondary positrons relative to that of the primary protons (and electrons) and thus explain the rise in the positron fraction observed by PAMELA above 10 GeV. We normalize the hadronic interaction rate by holding pion decay to be responsible for the gamma-rays detected by HESS from some SNRs. By simulating the spatial and temporal distrib…
The origin of the ultra high energy cosmic ray (UHECR) showers has remained as a mystery among particle physicists and astrophysicists. In low scale gravity models, where the neutrino-nucleon cross section rises to typical hadronic values at energies above $10^{20}$ eV, the neutrino becomes a candidate for the primary that initiates these showers. We calculate the neutrino-nucleon cross section at ultra high energies by assuming that it is dominated by the production of p-branes. We show, using a generalized Randall-Sundrum model, that the neutrino-nucleon cross-section at neutrino energies of…
Quantum Chromodynamics constitutes the quantum field theory of the strong interaction. Despite the success of this theory in the description of several hadronic processes, the elastic scattering is still a theoretical challenge. This process is characterized by a small transferred momentum and the perturbative techniques are not applicable. Although nonperturbative results have been obtained in recent years, we still do not have a full description within QCD of the quantities related to the elastic scattering, for example, $σ_{tot}$, the $ρ$ parameter and $σ_{el}$. In this thesis, the main int…
The momentum transfer $Δk$ required for a photon to scatter from a target and emerge as a $ρ^0$ decreases as the photon energy $k$ rises. For $k>3\times10^{14}$ eV, $Δk$ is small enough that the interaction cannot be localized to a single nucleus. At still higher energies, photons may coherently scatter elastically from bulk matter and emerge as a $ρ^0$, in a manner akin to kaon regeneration. Constructive interference from the different nuclei coherently raises the cross section and the interaction probability rises linearly with energy. At energies above $10^{23}$ eV, coherent conversion is t…
In high-energy hadron-hadron collisions, the dependence of the total cross-section ($σ_{tot}$) with the energy still constitutes an open problem for QCD. Phenomenological analyses usually relies on analytic parameterizations provided by the Regge-Gribov formalism and fits to the experimental data. In this framework, the singularities of the scattering amplitude in the complex angular momentum plane determine the asymptotic behavior of $σ_{tot}$ in terms of the energy. Usual applications connect simple and triple pole singularities with asymptotic power and logarithmic-squared functions of the …
The energy dependence of the total hadronic cross sections is caused by gluon bremsstrahlung which we treat nonperturbatively. It is located at small transverse distances about 0.3 fm from the valence quarks. The cross section of gluon radiation is predicted to exponentiate and rise with energy as s^Δ with Δ=0.17 +/- 0.01. The total cross section also includes a large energy independent Born term which corresponds to no gluon radiation. The calculated total cross section and the slope of elastic scattering are in good agreement with the data.
Recent data on Galactic cosmic-ray (CR) leptons and hadrons gave rise to two exciting problems: on the lepton side, the origin of the rise of the CR positron fraction e+/(e- + e+) at ~10 - 300 GeV of energy; on the hadron side, the nature of the spectral hardening observed in CR protons and nuclei at ~TeV energies. The lepton anomaly indicates the existence of a nearby e+/- source. It has been proposed that high-energy positrons can be produced inside nearby supernova remnants (SNRs) via interactions of CR hadrons with the ambient medium. A distinctive prediction of this mechanism is a high-en…
Most searches for ultra-high energy (UHE) astrophysical neutrinos look for radio emission from the electromagnetic and hadronic showers produced in their interactions. The radio frequency spectrum and angular distribution depend on the shower development, so are sensitive to the interaction cross sections. At energies above about 10^{16} eV (in ice), the Landau-Pomeranchuk-Migdal (LPM) effect significantly reduces the cross sections for the two dominant electromagnetic interactions: bremsstrahlung and pair production. At higher energies, above about 10^{20} eV, the photonuclear cross section b…
In models based on large extra dimensions where massive spin 2 exchange can dominate at high energies, the neutrino-proton cross section can rise to typical hadronic values at energies above 10^20 eV. The neutrino then becomes a candidate for the primary that initiates the highest energy cosmic ray showers. We investigate characteristics of neutrino-induced showers compared to proton-induced showers. The comparison includes study of starting depth, profile with depth, lateral particle distribution at ground and muon lateral distribution at ground level. We find that for cross sections above 20…
