Experimental data on total and differential elastic cross sections for $p+p(\bar{p})$, $n+p(\bar{p})$, $K^\pm+p$, $K^\pm+n$, $π^\pm+p$ starting from energy 3.5 GeV in CMS are used to determine parameters of vacuum contribution and parameters of basic non vacuum reggeons: $f$, $ω$, $ρ$ and $A_2$. It is argued that non vacuum contributions to proton-proton and proton-neutron collisions correspond to spectrum in which baryon number is moved from the fragmentation region to central region in rapidity space. In this case it is possible that chemical potential is increased in central region of spectrum of nucleus-nucleus interaction at low energies. This effect might be important for facilities FAIR and NICA.
We derive an equation determining the small-x evolution of the F_2 structure function of a large nucleus which includes all multiple pomeron exchanges in the leading logarithmic approximation using Mueller's dipole model. We show that in the double leading logarithmic limit this evolution equation reduces to the GLR equation.
Some results on the perturbative Regge asymptotics are reviewed. The concepts of the reggeon interaction approach and the double logarithmic approximation are outlined. Contribution to the Zeuthen Workshop on QCD and QED at higher order, Rheinsberg, April 1996.
We analyze the evolution equation describing all multiple hard pomeron exchanges in a hadronic or nuclear structure functions that was proposed earlier. We construct a perturbation series providing us with an exact solution to the equation outside of the saturation region. The series demonstrates how at moderately high energies the corrections to the single BFKL pomeron exchange contribution which are due to the multiple pomeron exchanges start unitarizing total deep inelastic scattering cross section. We show that as energy increases the scattering cross section of the quark-antiquark pair of…
One-to-one correspondence between dual diagrams of dual resonance model and QCD based color diagrams describing non vacuum exchanges in pi+ pi-, pi+- p, p anti p interactions is discussed. Both for dual and color diagrams there are state with quark-antiquark in t channel and state, in which only coherent quark string exists, in s channel. There are no such dual diagrams in pp interaction. Color diagram for pp interaction was found basing on principle of conformity. Secondary hadrons spectrum, obtained from this diagram, has nucleon in its central region. This effect may lead to increase of bar…
We apply our recently formulated Gluon Exchange Model (GEM) to baryon production in proton-nucleus reactions involving N>1 proton-nucleon collisions. We propose a description scheme for the process of soft color octet (gluon) exchange, based on the assumption that probabilities to form an effective diquark are equal for all allowed pairs of quarks. The latter effective diquark can form either from two valence, one valence and one sea, or from two sea quarks. Consequently we calculate the probabilities for different color configurations involving diquarks of valence-valence, valence-sea and sea…
Employing the Worldline casting of the Dosch-Simonov Stochastic Vacuum Model(SVM) for QCD, a simulated meson-meson scattering is studied in the Regge kinematical regime. The process is modelled in terms of the "helicoidal" Wilson contour first introduced by Janic and Peschanski in a related study based on an AdS/CFT-type approach. Using lattice supported estimations for the behavior of a two-point, field strength correlation function, as defined in the framework of the SVM, the reggeon slope and intercept are calculated in a semiclassical approximation. The resulting values are in good agreeme…
We present our recent progress in the description of neutrino-nucleus interaction in the GeV region, of interest for ongoing and future oscillation experiments. In particular, we discuss the weak excitation of two-particle-two-hole states induced by meson exchange currents in a fully relativistic framework. We compare the results of our model with recent measurements of neutrino scattering cross sections, showing the crucial role played by two-nucleon knockout in the interpretation of the data.
We give a compact expression for the unpolarised differential cross section for muon-proton scattering in the one photon exchange approximation. The effect of adding the vacuum polarisation amplitude to the no-spin-flip amplitude for one photon exchange is calculated at small energies and scattering angles and is found to be negligible for present experiments.
We study the coherent final state interaction of an energetic parton produced in AA collisions caused by the change in the cutoff scale and running coupling constant from the vacuum to QGP. We demonstrate that the contribution of this new mechanism to the energy loss may be of the order of magnitude of the induced gluon radiation. However, an accurate evaluation of this medium effect is a difficult task because there is a strong cancellation between the cutoff and running coupling constant effects. The uncertainties in the contribution of the coherent final state interaction restrict strongly …
The total and angular differential cross sections of the coherent process $\bar p + {}^AZ \to {}^A_Λ(Z-1) + \barΛ$ are evaluated at the beam momenta $1.5\div20$ GeV/c within the meson exchange model with bound proton and $Λ$-hyperon wave functions. It is shown that the shape of the beam momentum dependence of the hypernucleus production cross sections with various discrete $Λ$ states is strongly sensitive to the presence of the scalar $κ$-meson exchange in the $\bar p p \to \barΛΛ$ amplitude. This can be used as a clean test of the exchange by scalar $πK$ correlation in coherent $\bar p A$ rea…
The effect of vacuum polarization on the parity violating asymmetry in the elastic electron-nucleus scattering is considered. Calculations are performed in the high-energy approximation with an exact account for the electric field of the nucleus. It is shown that the radiative correction to the parity violating asymmetry is logarithmically enhanced and the value of the correction is about -1%.
In this paper we have demonstrated the double Q^2-rescaling model (DQ^2RM) of parton distribution functions of nucleon bounded in nucleus. With different x-region of l-A deep inelastic scattering process we take different approach: in high x-region (0.1\le x\le 0.7) we use the distorted QCD vacuum model which resulted from topologically multi -connected domain vacuum structure of nucleus; in low x-region (10^{-4}\le x\le10^{-3}) we adopt the Glauber (Mueller) multi- scattering formula for gluon coherently rescattering in nucleus. From these two approach we justified the rescaling parton distri…
The recent analysis of nuclear distortions in DIS off nuclei revealed a breaking of the conventional hard factorization for multijet observable. The related pQCD analysis of distortion effects for jet production in nucleus-nucleus collisions is as yet lacking. As a testing ground for such an analysis we consider the Abelian problem of higher order Coulomb distortions of the spectrum of lepton pairs produced in peripheral nuclear collisions. We report an explicit calculation of the contribution to the lepton pair production in the collision of two photons from one nucleus with two photons from …
We propose a new model for a homogeneous description of hadron-hadron and hadron-nucleus collisions, the Gluon Exchange Model, fundamentally based on color octet (gluon) exchange. In proton-proton collisions we provide an exact description of the final state proton and neutron spectrum including the proton diffractive peak. In proton-nucleus reactions we find that the projectile proton diquark cannot survive in more than about half of multiple proton-nucleon processes and consequently must be very frequently disintegrated, leading to long transfers of baryon number over rapidity space.
We review some recent progress in the study of electroweak interactions in nuclei within the SuSAv2-MEC model. The model has the capability to predict (anti)neutrino scattering observables on different nuclei. The theoretical predictions are compared with the recent T2K $ν_μ-^{16}$O data and good agreement is found at all kinematics. The results are very similar to those obtained for $ν_μ-^{12}$C scattering, except at low energies, where some differences emerge. The role of meson-exchange currents in the two-particle two-hole channel is analyzed in some detail. In particular it is shown that t…
The total cross sections of interaction of relativistic π^+π^- atom with ordinary atoms are obtained in the eikonal approach, which takes into consideration all multiphoton exchange processes. Contribution of these processes strongly depends on the atom nucleus charge Z and varies from 1.5% for Titanium (Z=22) to 14% for Tantalum (Z=73)
Background: Proton-nucleus collisions have been used as a intermediate baseline for the determination of cold medium effects. They lie between proton-proton collisions in vacuum and nucleus-nucleus collisions which are expected to be dominated by hot matter effects. Modifications of the quark densities in nuclei relative to those of the proton are well established although those of the gluons in the nucleus are not well understood. We focus on the effect of these on quarkonium production in proton-lead collisions at the LHC at a center of mass energy of 5.02 TeV.
We argue that the large suppression of the $ψ(2S)$ inclusive cross-section relative to the $J/ψ$ inclusive cross-section in proton-nucleus (p+A) collisions can be attributed to factorization breaking effects in the formation of quarkonium. These factorization breaking effects arise from soft color exchanges between charm-anticharm pairs undergoing hadronization and comoving partons that are long-lived on time scales of quarkonium formation. We compute the short distance pair production of heavy quarks in the Color Glass Condensate (CGC) effective field theory and employ an improved Color Evapo…
We consider high energy collisions of two shock waves in AdS_5 as a model of ultrarelativistic nucleus-nucleus collisions in the boundary theory. We first calculate the graviton field produced in the collisions in the NLO and NNLO approximations, corresponding to three- and four-graviton exchanges with the shock waves. We then consider the asymmetric limit where the energy density in one shock wave is much higher than in the other one. In the boundary theory this setup corresponds to proton-nucleus collisions, with the nucleus being the denser of the two shock waves and the proton being the le…
In a previous paper, Symmetry Finder (SF) method is proposed to find the reparametrization symmetry of the state-exchange type in neutrino oscillation in matter. It has been applied successfully to the 1-2 state exchange symmetry in the DMP perturbation theory, yielding the eight symmetries. In this paper, we apply the SF method to the atmospheric-resonance perturbation theory to uncover the 1-3 state relabeling symmetries. The pure 1-3 state symmetry takes the unique position that it is practically impossible to formulate in vacuum under the conventional choice of the flavor mixing matrix. In…
Parity nonconservation due to the nuclear weak charge is considered. We demonstrate that the radiative corrections to this effect due to the vacuum fluctuations of the characteristic size larger than the nuclear radius $r_0$ and smaller than the electron Compton wave-length $λ_C$ are enhanced because of the strong electric field of the nucleus. The parameter that allows one to classify the corrections is the large logarithm $\ln(λ_C/r_0)$. The vacuum polarization contribution is enhanced by the second power of the logarithm. Although the self-energy and the vertex corrections do not vanish, th…
We demonstrate that jet observables are highly sensitive to the characteristics of the vacuum and the in-medium QCD parton showers and propose techniques that exploit this sensitivity to constrain the mechanism of quark and gluon energy loss in strongly-interacting plasmas. As a first example, we calculate the inclusive jet cross section in high-energy nucleus-nucleus collisions to ${\cal O}(α_s^3)$. Theoretical predictions for the medium-induced jet broadening and the suppression of the jet production rate due to cold and hot nuclear matter effects in Au+Au and Cu+Cu reactions at RHIC are pre…
The inclusive double Pomeron exchange cross section for heavy quark pair production is calculated for nucleus-nucleus collisions at the LHC. The present estimate is based on hard diffractive factorization, corrected by absorptive corrections and nuclear effects. The theoretical uncertainties for nuclear collisions are investigated and a comparison to other approaches is presented. The production channels producing a similar final state configuration are discussed as well.
We develop a new approach for calculating the spin-independent 2-neutrino exchange potential (2-NEP) between non-relativistic fermions which places emphasis on the neutrino vacuum state, an area of theoretical interest in recent years. The 2-NEP is a natural probe of fundamental issues of neutrino physics such as neutrino masses, flavor mixing, the number of neutrino flavors, neutrino nature (Dirac or Majorana), $CP$-violation, and the neutrino vacuum state. We explore the dependence of the 2-NEP on the mixing of neutrino mass states assuming normal and inverted mass ordering for nucleon-nucle…
The cross sections for the glueball candidates production in quasi-real photon-photon collisions and on central diffraction processes, i.e. double Pomeron exchange, in heavy ion interactions at RHIC and LHC are computed. The rates for these distinct production channels are compared and they may be a fruitful approach to the investigation of glueballs.
We calculate O(alpha_S^4 m) and O(alpha_S^4 m log(alpha_S)) corrections to the quarkonium 1S energy level analytically, which have been overlooked in recent studies. These are the contributions from one Coulomb-gluon exchange with the 1-loop vacuum polarization insertion. A part of the corrections was computed numerically some time ago; we correct its error.
High-energy open beauty photoproduction probes the vacuum exchange at distances $\sim 1/m_b$ and detects significant corrections to the BFKL asymptotics coming from the subleading vacuum poles. We show that the interplay of leading and subleading vacuum exchanges gives rise to the cross section $σ^{b\bar b}(W)$ growing much faster than it is prescribed by the exchange of the leading pomeron trajectory with intercept $α_{\Pom}(0)-1=Δ_{\Pom}=0.4$. Our calculations within the color dipole BFKL model are in agreement with the recent determination of $σ^{b\bar b}(W)$ by the H1 collaboration. The co…
I will discuss how the non-vacuum, quark-antiquark Reggeon-exchange contribution to meson-meson elastic scattering, at high energy and low tranferred momentum, can be related to the path-integral of a certain Wilson-loop expectation value over the trajectories of the exchanged fermions. Making use of this representation, I will show how a linear Regge trajectory is obtained through gauge/gravity duality and the use of minimal surfaces.
It has been argued that the leading scalar-isoscalar WIMP-nucleus interactions receive parametrically enhanced contributions in the context of nuclear effective field theories. These contributions arise from meson-exchange currents (MECs) and potentially modify the impulse approximation estimates of these interactions by 10--60%. We point out that these MECs also contribute to the quark mass dependence of nuclear binding energies, that is, nuclear σ-terms. In this work, we use recent lattice QCD calculations of the binding energies of the deuteron, He-3 and He-4 at pion masses near 500 MeV and…
We study in detail the influence of the nuclear form factor both on the Born cross section and on the Coulomb corrections to the photo-production of muon pairs off heavy nuclei (gamma Z -> mu+ mu- Z$) and in heavy-ion collisions (ZZ -> ZZ mu+ mu-). Our findings indicate a number of issues which have not been sufficiently described as yet in the literature: (i) the use of a realistic form factor, based on the Fermi charge distribution for the nucleus, is absolutely indispensable for reliable theoretical predictions; (ii) we checked quantitatively that the equivalent photon approximation has a v…
The results of the microscopic transport calculations of $\bar p$-nucleus interactions within a GiBUU model are presented. The dominating mechanism of hyperon production is the strangeness exchange processes $\bar K N \to Y π$ and $\bar K N \to ΞK$. The calculated rapidity spectra of $Ξ$ hyperons are significantly shifted to forward rapidities with respect to the spectra of $S=-1$ hyperons. We argue that this shift should be a sensitive test for the possible exotic mechanisms of $\bar p$-nucleus annihilation. The production of the double $Λ$-hypernuclei by $Ξ^-$ interaction with a secondary ta…
We have extended our model for charged current neutrino-nucleus interactions to neutral current reactions. For the elementary neutrino-nucleon interaction, we take into account quasielastic scattering, Delta excitation and the excitation of the resonances in the second resonance region. Our model for the neutrino-nucleus collisions includes in-medium effects such as Fermi motion, Pauli blocking, nuclear binding, and final-state interactions. They are implemented by means of the Giessen Boltzmann-Uehling-Uhlenbeck (GiBUU) coupled-channel transport model. This allows us to study exclusive channe…
Ultraperipheral collisions at collider energies are a useful tool to study photon-hadron (proton/nucleus) and photon-photon interactions in a hitherto unexplored energy regime. Theoretical tools to study these processes are briefly described. Some current results and problems are discussed
We investigate the production of charm-baryon hypernucleus $^{16}_{Λ_c^+}$O in the antiproton - $^{16}$O collisions within a fully covariant model that is based on an effective Lagrangian approach. The explicit ${\bar Λ}_c^ - Λ_c^+$ production vertex is described by the $t$-channel $D^0$ and $D^{*0}$ meson-exchanges in the initial collision of the incident antiproton with one of the protons of the target nucleus. The $Λ_c^+$ bound state spinors as well as the self-energies of the exchanged mesons employed in our calculations are derived from the quark-meson coupling model. The parameters of va…
A weakly-interacting massive particle (WIMP) is perhaps the most promising candidate for the dark matter in the Galactic halo. The WIMP detection rate in laboratory searches is fixed by the cross section for elastic WIMP-nucleus scattering. Here we calculate the contribution to this cross section from two-nucleon currents from pion exchange in the nucleus, and show that it may in some cases be comparable to the one-nucleon current that has been considered in prior work, and perhaps help resolve the discrepancies between the various direct dark-matter search experiments. We provide simple expre…
We consider a set of radiative contributions from one-loop lepton vacuum polarization to the hyperfine splitting of true muonium. Improving previous results, we obtain values for the electron-loop coefficients and extract their leading dependence upon $β=m_μ/m_e$. The coefficients are $C^μ_{20,1{\rm VPCT}}=0.734931603β$, $C^μ_{20,1{\rm VPCA}}=0.551198702β$, and $C^μ_{20,1{\rm VPT}}=0.419149715β$. The mass-independent contribution from three one-loop vacuum polarization is $C_{40,{\rm VPX}}=\frac{1}{127575}\left(-5255-2016π^2+51840ζ(3)\right)$. Contributions from $τ$ up to $\mathcal{O}(m_μα^8)$…
Microscopic calculation of two-particle-two-hole meson-exchange currents in $^{40}$Ar and asymmetric scaling properties for neutrino and electron scattering
The exclusive $K^+$ meson production in a proton-nucleus collision, leading to two body final states, is investigated in a fully covariant two-nucleon model based on the effective Lagrangian picture. The explicit kaon production vertex is described via creation, propagation and decay into relevant channel of $N^*$(1650), $N^*$(1710) and $N^*$(1720) intermediate baryonic states in the initial collision of the projectile nucleon with one of its target counterparts which is modeled by the one-pion exchange process. The calculated cross sections show strong sensitivity to the medium effects on pio…
Interpretation of current and future neutrino oscillation and electron scattering experiments requires knowledge of lepton-nucleon and lepton-nucleus interactions at the percent level. We study the exchange of photons between charged particles and the nuclear medium for (anti)neutrino-, electron-, and muon-induced reactions inside a large nucleus. While quantum electrodynamics (QED)-medium contributions are formally suppressed by two powers of the electromagnetic coupling constant $α$ when compared to the leading-order cross sections, low-energy modes and the nuclear size enhance the effect by…
We study the $\bar D D$ (${\bar D}^0 D^0$ and $D^-D^+$) charm meson pair production in antiproton (${\bar p}$) induced reactions on nuclei at beam energies ranging from threshold to several GeV. Our model is based on an effective Lagrangian approach that has only the baryon-meson degrees of freedom and involves the physical hadron masses. The reaction proceeds via the $t$-channel exchanges of $Λ_c^+$, $Σ_c^+$, and $Σ_c^{++}$ baryons in the initial collision of the antiproton with one of the protons of the target nucleus. The medium effects on the exchanged baryons are included by incorporating…
It is shown that the dynamical observables calculated with the point form relativistic quantum mechanics incorporate effects of particle-antiparticle creation from the vacuum by interactions. The electromagnetic observables obtained with the point form impulse approximation include contributions from the ``pair'' exchange currents that are associated with the interactions between particles. This implies that the recently calculated nucleon electromagnetic formfactors with the chiral constituent quark model automatically take into account effects of ``pair'' exchange currents that are associate…
We review the nuclear parton distribution functions computed on the basis of our microscopic model taking into account a number of nuclear effects including Fermi motion and nuclear binding, nuclear meson-exchange currents, off-shell corrections to bound nucleon distributions and nuclear shadowing. We discuss applications to a number of different processes including lepton-nucleus deep inelastic scattering, proton-nucleus Drell-Yan lepton pair production at Fermilab, as well as $W^\pm$ and $Z^0$ boson production in proton-lead collisions at the LHC.
We analyze the timing of photons observed by the MAGIC telescope during a flare of the active galactic nucleus Mkn 501 for a possible correlation with energy, as suggested by some models of quantum gravity (QG), which predict a vacuum refractive index \simeq 1 + (E/M_{QGn})^n, n = 1,2. Parametrizing the delay between gamma-rays of different energies as Δt =\pmτ_l E or Δt =\pmτ_q E^2, we find τ_l=(0.030\pm0.012) s/GeV at the 2.5-sigma level, and τ_q=(3.71\pm2.57)x10^{-6} s/GeV^2, respectively. We use these results to establish lower limits M_{QG1} > 0.21x10^{18} GeV and M_{QG2} > 0.26x10^{11} G…
