N. Tyurin

The PHENIX Electromagnetic Calorimeter (EMCal) is used to measure the spatial position and energy of electrons and photons produced in heavy ion collisions. It covers the full central spectrometer acceptance of 70°⩽θ⩽110° with two walls, each subtending 90° in azimuth. One wall comprises four sectors of a Pb-scintillator sampling calorimeter and the other has two sectors of Pb-scintillator and two of a Pb-glass Cherenkov calorimeter. Both detectors have very good energy, spatial and timing resolution, while the Pb-scintillator excels in timing and the Pb-glass in energy measurements. Also, having two detectors with different systematics increases the confidence level of the physics results. Design and operational parameters of the Pb-scintillator, Pb-glass and special readout electronics for EMCal are presented and running experience during the first year of data taking with PHENIX is discussed. Some examples of data taken during the first run are shown.

Proceeding from optical analogy we propose a new physical interpretation of unitarity saturation leading to antishadowing as a reflective scattering. This interpretation of antishadowing is related to the nonperturbative aspects of strong interactions and follows from the specific property of the unitarity saturation when elastic S-matrix S(s, b)| b = 0 → -1 at s→∞. The analogy with Berry phase and experimental consequences of the proposed interpretation as reflective scattering at the LHC and in the cosmic rays studies are discussed.

We consider a nonperturbative mechanism for hyperon polarization in inclusive production at moderate transverse momenta. The main role belongs to the orbital angular momentum and the polarization of the strange quark-antiquark pairs in the internal structure of the constituent quarks. We consider a nucleon as a core consisting of the constituent quarks embedded into a quark condensate. The nonperturbative hadron structure is inspired by the results of the chiral quark models.

We point out the several experimental manifestations of the new reflective scattering mode in elastic scattering and multiparticle production at the LHC energy range.

A gradual transition to the reflecting scattering mode developing already at the LHC energies is affecting multiparticle production dynamics, in particular, relation of the centrality with the impact parameter values of pp-collisions. We discuss the issues in the framework of the geometrical picture for the multiparticle production processes proposed by Chou and Yang. We consider effects of reflective scattering mode presence for the inclusive cross-sections.

Hadron scattering at large and small distances is simultaneously described in the framework of the unitarization method based on a generalized reaction matrix. The assumed dynamics of hadron interactions is inspired by the ideas of the chiral quark models. The proposed model for hadron interactions is based on geometrical notions of the interactions of constituent quarks similar to those used by Chou and Yang for the description of hadronic interactions. This model allows us to reproduce the ${\mathrm{ln}}^{2}s$ growth of the total cross sections as well as regularities in the behavior of differential cross sections, in particular, its power-law falloff at fixed angles. It also allows us to get the correct values for the total cross-section ratios of hyperon-proton and proton-proton interactions and to estimate the total cross-section values for interactions of the hadrons containing heavy quarks.

We discuss various aspects of the multiparticle production processes at the LHC energy range with emphasis on the collective effects associated with appearance of the new scattering mode, which corresponds to the reflective scattering and its impact on multiparticle production processes.

Deep--elastic scattering and its role in discrimination of the possible absorptive and reflective asymptotic scattering mechanisms are discussed with emphasis on the difference in the experimental signatures related to production processes.

We discuss energy dependence of rapidity gap survival probability in the double-pomeron exchange processes with account of the reflective scattering effects.

We consider mechanism for one-spin asymmetries observed in inclusive hadron production. The main role belongs to the orbital angular momentum of the quark-antiquark cloud in the internal structure of constituent quarks. We argue that the origin of the asymmetries in pion production is a result of retaining of this internal angular orbital momentum by the perturbative phase of QCD under transition from the non-perturbative phase. The non-perturbative hadron structure is based on the results of chiral quark models. PACS number(s): 11.30.Qc, 12.40.Pp, 13.75.Ni, 13.88.+e

We discuss directed flow v 1 , an observable introduced for the description of nucleus collisions. We consider its possible origin in hadronic reactions as a result of rotation of the transient matter and trace the analogy with nucleus collisions.

New data on measuring the ratio of the real to imaginary part of the forward scattering amplitude, ϱpp (√s=546 GeV)=0.24±0.04, have been considered. This result is shown to agree with the behaviour of σt(s), predicted by the U-matrix model. The possibility of a transition to the antishadow scattering mode at superhigh energies is discussed.

The pre-asymptotic behaviour of total and elastic crosssections is considered on the basis of the quark model for theU-matrix.

We discuss the possibility of changing the energy dependence of the mean multiplicity, i.e. slow down of its growth at the LHC energies due to a gradual transition to the reflecting scattering mode.

We discuss discrimination of the scattering mechanisms on the basis of functional dependencies of the large-t elastic scattering suggested by the recent data from the TOTEM experiment. It is shown that Orear exponent is in a better agreement with the data than the power-like dependence used by the TOTEM. This implies that the collective dynamics is dominating over the point-like mechanism related to the scattering of the proton constituents. We also emphasize that vanishing of the helicity-flip amplitudes contributions at the LHC energies would result in appearance of the dip–bump structures at higher values of transferred momenta.

We emphasize that recently observed regularities in hadron interactions and deep-inelastic scattering are of a preasymptotic nature and it is impossible to draw conclusions on the true asymptotic behavior of observables without unitarization procedures. Unitarization is important and changes the scattering picture drastically.

We propose a dynamical model for the unpolarized generalized parton distribution function (GPD) based on impact parameter representation and discuss its x and t dependencies at large and small values of these variables.

Deep-inelastic scattering at low Bjorken x and elastic vector meson electroproduction are analyzed on the basis of the off-shell s-channel unitarity. We discuss behavior of the total cross-section of virtual photon-proton scattering and obtain, in particular, that the exponent in the power-like dependence of $\sigma^{tot}_{\gamma^* p}$ is related to the interaction radius of a constituent quark. The explicit mass dependence of the exponent in the power energy behavior of the vector meson electroproduction has been obtained. Angular distributions at large momentum transfers are considered. The energy dependence of the total cross-section of $\gamma^*\gamma^*$-interactions is also obtained.

We discuss how the reflective scattering would affect elastic scattering in the region of small and moderate values of -t, in particular, we demonstrate that diffractive pattern in the angular distribution will be kept in a modified form.

We discuss recent experimental results from RHIC where the flat transverse momentum dependence of a single-spin asymmetry has been found in inclusive production of neutral pions. This dependence takes place in a wide region of the transverse momenta up to $p_T=10$ GeV/c. We emphasize that similar dependence has been predicted in the nonperturbative spin filtering mechanism for the single-spin asymmetries in hadron interactions and present some implications for this mechanism from the new experimental data.

We consider collective effects in pp-collisions at the LHC energies related to presence of the large orbital angular momentum in the initial state and role of this orbital momentum in the elliptic flow behavior.

Numerical predictions for the global characteristics of proton–proton interactions are given for the LHC energy. Possibilities for the discovery of the antishadow scattering mode and its physical implications are discussed.

We discuss how confinement property of QCD results in the rational unitarization scheme and how unitarity saturation leads to the appearance of a hadron liquid phase at very high temperatures.

We discuss a nonperturbative mechanism for generation of the single-spin asymmetries in hadron interactions. It is based on the chiral quark model combined with unitarity and impact parameter picture and provides explanation for the experimental regularities observed under the measurements of the spin asymmetries.

Motivated by the first measurements of the experiment CMS at the LHC at [Formula: see text] and 2.36 TeV, we discuss energy dependence of average transverse momentum of the secondary particles in hadron production in pp-collisions. We suggest a possible explanation of this dependence as a result of collective rotation of the transient state and associate its further possible decrease with flattening off at higher energies with transition to the genuine QGP state of matter.

For the inelastic diffraction, we obtain an upper bound valid in the whole range of the elastic scattering amplitude variation allowed by unitarity. We discuss the energy dependence of the inelastic diffractive cross-section on the base of this bound and recent LHC data.

We discuss a possible explanation of the double-ridge observation in pPb-collisions at the LHC emphasizing that this double structure in the two-particle correlation function can result from the rotation of the transient state of matter.

It is argued that the expected turn-down in $x- Q^2$ of the cross sections (structure functions $F_2(x,Q^2)$), assumed to result from the saturation of parton densities in the nucleon, is related to a phase transition from the (almost) ideal partonic gas, obeying Bjorken scaling, to a partonic "liquid". This can be quantified in the framework of statistical models, percolation and other approaches to collective phenomena of the strongly interacting matter. Similarities and differences between the case of lepton-hadron, hadron-hadron and nuclear collisions are discussed.

We discuss effects of reflective scattering for heavy nuclei collisions and the deconfined matter formation at the LHC and asymptotical energies. Reflective scattering in hadron collisions leads to decreasing matter density with energy beyond the LHC energies. Limiting form of energy dependence of hadron density is obtained.

Abstract In the approach based on the QFT equation for the scattering amplitude we consider polarization behaviour at large angles for pp and πN scattering. It is shown that polarization may get a considerable value and be a nonvanishing function of s . The relations between the s dependences of polarization, spin correlation parameter A nn and differential cross section d σ (90°)/d t are discussed.

The perturbative QCD status is considered in the review from the point of view of the polarization experiments results. It is stressed that at present there is a confrontation between the perturbative QCD and the experimental data on studying spin phenomena.

On the basis of the mechanism proposed earlier for one-spin asymmetries in inclusive hadron production we consider OZI--suppressed process of $\varphi$-meson production $pp\rightarrow \varphi X$ and asymmetry $A_N(\varphi)$ in this process. The main role in generation of this asymmetry belongs to the orbital angular momentum of strange quark-antiquark cloud in internal structure of constituent quarks.

The specific effects of the reflective scattering (antishadowing) related to the spin correlations in the top quark production at the LHC are considered. Account for those effects is important in the searches for the signatures of the extra dimensiones. It is shown that significant spin correlations could arise at the LHC energies due to reflective scattering and those can affect the signals of the extra dimensions.

We discuss effects of reflective scattering for hadron and heavy nuclei collisions at the LHC and asymptotical energies. It is shown that the reflective scattering might lead to decreasing matter density with energy beyond the LHC energies. Limiting form of energy dependence of hadron density is obtained. Unitarity upper bound for the absolute value of the real part of elastic scattering amplitude and two-particle inelastic binary reactions amplitudes in impact parameter representation is two times less than the corresponding bound for the imaginary part of the elastic scattering amplitude. The former limit restricts a possible odderon contribution.

The dynamics of spin effects in hard hadron processes is discussed. Possibilities for the experimental study of the effects by means of accelerated, polarised proton beams are considered.

We asses a role of the double helicity-flip amplitudes in small-angle elastic pp-scattering and obtain a new unitary bound for the double helicity-flip amplitude F2 in elastic pp-scattering at small values of t on the basis of the U-matrix method of the s-channel unitarization.

It is shown that the universality of the initial and final state interactions responsible for the transition between the on-- and off--mass shell states leads to the energy independence of the ratio of exclusive $\rho$ electroproduction cross section to the total cross section. It is demonstrated that the above universality and explicit mass dependence of the exponent in the power--like energy behavior of the cross-section obtained in the approach based on unitarity is in a quantitative agreement with the high--energy HERA experimental data. We discuss also HERA results on angular distributions of vector--meson production.

A gradual transition to the reflecting scattering mode developing already at the LHC energies is affecting multiparticle production dynamics, in particular, relation of the centrality with the impact parameter values of $pp$--collisions. We discuss the issues in the framework of the geometrical picture for the multiparticle production processes proposed by Chou and Yang. We consider effects of reflective scattering mode presence for the inclusive cross-sections.

We discuss collective effects in pp-collisions at the LHC energies and derive an upper bound for the anisotropic flow coefficients v n . A possibility of its verification via comparison with the measurements of v 2 is considered. We use an assumption on the relation of the two-particle correlations with the rotation of the transient state of matter.

We consider the impact parameter dependence of the polarized and unpolarized structure functions. Unitarity does not allow factorization of the structure functions over the Bjorken x and the impact parameter b variables. On the basis of the particular geometrical model approach we conclude that the spin of constituent quarks may have a significant orbital angular momentum component which can manifest itself through the peripherality of the spin-dependent structure functions.

It is argued that directed flow $v_1$, the observable introduced for description of nucleus collisions, can be used for the detection of the nature of state of the matter in the transient state of hadron and nuclei collisions. We consider a possible origin of the directed flow in hadronic reactions as a result of rotation of the transient matter and trace analogy with nucleus collisions. Our proposal it that the presence of directed flow can serve as a signal that transient matter is in a liquid state.

We propose a model for the unpolarized generalized parton distribution function (GPD) based on impact parameter representation and discuss its x and t dependencies at large and small values of these variables.

It is argued that the expected turn-down in $x- Q^2$ of the cross sections (structure functions $F_2(x,Q^2)$), assumed to result from the saturation of parton densities in the nucleon, is related to a phase transition from the (almost) ideal partonic gas, obeying Bjorken scaling, to a partonic 'liquid'. This can be quantified in the framework of statistical models, percolation and other approaches to collective phenomena of the strongly interacting matter. Similarities and differences between the case of lepton-hadron, hadron-hadron and nuclear collisions are discussed.

We consider the low-$x$ behavior of the spin structure functions ${g}_{1}(x)$ and ${h}_{1}(x)$ in the unitarized chiral quark model that combines the ideas on constituent quark structure of hadrons with a geometrical scattering picture and unitarity. A nondiffractive singular low-$x$ dependence of ${g}_{1}^{p}(x)$ and ${g}_{1}^{n}(x)$ is obtained and a diffractive type smooth behavior of ${h}_{1}(x)$ is predicted at small $x.$ A comparison with the experimental data is given. The estimations for the double-spin asymmetries in the low-mass Drell-Yan production at BNL RHIC in the central region are presented also.

Starting from rotational invariance we derive sum rules for the single-spin asymmetries in inclusive production and binary processes. We also get sum rules for spin correlation parameters in elastic pp-scattering.

We consider the physics motivations and perspectives for the study of spin phenomena at the future high energies accelerators. The possibilities to use the already operating machines are also discussed. It is emphasized that the present status of QCD spin studies necessarily requires a wide range of spin measurements

Deep-inelastic scattering at low x and elastic vector meson production are considered on the basis of the off-shell extension of the s-channel unitarity. We discuss behavior of the structure function F_2(x,Q^2) at low x and the total cross-section of virtual photon-proton scattering and obtain, in particular, the dependence sigma^{tot}_{gamma^* p}\sim (W^2)^{lambda(Q^2)} where exponent lambda(Q^2) is related to the interaction radius of a constituent quark. The energy dependence of the total cross-section of gamma^*gamma^*-interactions is calculated. The explicit mass dependence of the exponent in the power energy behavior of the vector meson production in the processes of virtual photon interactions with a proton gamma^*p to Vp has been obtained. We also consider angular distributions at large momentum transfers.

We consider angular dependence of the diffractive dissociation processes at high energies. It appeared that angular dependence of the diffractive dissociation has no dip and bump structure at the LHC energies and would show a smooth power-like decrease with $t$. The normalized differential cross-section has a scaling behavior and depends on the ratio $-t/M^2$ only. These results reflect general trends of unitarity limitations at high energies and are realized within the chiral quark model with unitarization performed through the generalized reaction matrix.

We consider impact parameter dependence of the polarized and unpolarized parton densities. Unitarity does not allow factorization of these structure functions over the Bjorken x and the impact parameter b variables. On the basis of the particular geometrical model approach we conclude that spin of constituent quark may have a significant orbital angular momentum component which can manifest itself through the peripherality of the spin dependent structure functions.

We consider consequences of violation of the black disk limit possibly revealed by the new CDF measurements of the total, elastic and diffractive cross-sections.