Search

The observed enhancement of low-kT photons in comparison with incorrect calculations, should not be treated as a puzzle. The paper by Low considered a large rapidity gap process of diffractive excitation of a hadron, h -> h+\gamma, rather than multiple hadron production spanning all over the rapidity interval between colliding hadrons. The optical theorem connects these two processes, and what is inner bremsstrahlung, suppressed according to Low, corresponds to radiation from final state hadrons. Thus, the main result of the Low theorem, based on gauge invariance of the diffractive bremsstrahlung amplitude, supplemented with the optical theorem, contradicts the so-called bremsstrahlung model. The latter has been used for comparison with data, leading to the longstanding soft photon puzzle., Comment: 8 pages 8 figures

We propose to create a secondary beam of neutral kaons in Hall D at Jefferson Lab to be used with the GlueX experimental setup for strange hadron spectroscopy. The superior CEBAF electron beam will enable a flux on the order of $1\times 10^4~K_L/sec$, which exceeds the flux of that previously attained at SLAC by three orders of magnitude. The use of a deuteron target will provide first measurements ever with neutral kaons on neutrons. The experiment will measure both differential cross sections and self-analyzed polarizations of the produced $\Lambda$, $\Sigma$, $\Xi$, and $\Omega$ hyperons using the GlueX detector at the Jefferson Lab Hall D. The measurements will span CM $\cos\theta$ from $-0.95$ to 0.95 in the range W = 1490 MeV to 2500 MeV. The new data will significantly constrain the partial wave analyses and reduce model-dependent uncertainties in the extraction of the properties and pole positions of the strange hyperon resonances, and establish the orbitally excited multiplets in the spectra of the $\Xi$ and $\Omega$ hyperons. Comparison with the corresponding multiplets in the spectra of the charm and bottom hyperons will provide insight into he accuracy of QCD-based calculations over a large range of masses. The proposed facility will have a defining impact in the strange meson sector through measurements of the final state $K\pi$ system up to 2 GeV invariant mass. This will allow the determination of pole positions and widths of all relevant $K^\ast(K\pi)$ $S$-,$P$-,$D$-,$F$-, and $G$-wave resonances, settle the question of the existence or nonexistence of scalar meson $\kappa/K_0^\ast(700)$ and improve the constrains on their pole parameters. Subsequently improving our knowledge of the low-lying scalar nonet in general., Comment: Final version of the KLF Proposal [C12-19-001] approved by JLab PAC48. The intermediate version of the proposal was posted in arXiv:1707.05284 [hep-ex]. 103 pages, 52 figures, 8 tables, 324 references. Several typos were fixed

We study the single-spin asymmetry, $A_N(t)$, arising from Coulomb-nuclear interference (CNI) at small 4-momentum transfer squared, $-t=q^2$, aiming at explanation of the recent data from the PHENIX experiment at RHIC on polarized proton-nucleus scattering, exposing a nontrivial $t$-dependence of $A_N$. We found that the failure of previous theoretical attempts to explain these data, was due to lack of absorptive corrections in the Coulomb amplitude of $pA$ elastic scattering. Our prominent observation is that the main contribution to $A_N(t)$ comes from interference of the amplitudes of ultra-peripheral and central collisions., Comment: 4 pages, EDS Blois 2017, Prague, Czech Republic, June 26-30, 2017

We present a detailed study of open heavy flavor production in high-energy $pp$ collisions at the LHC in the color dipole framework. The transverse momentum distributions of produced $b$-jets, accounting for the jet energy loss, as well as produced open charm $D$ and bottom $B$ mesons in distinct rapidity intervals relevant for LHC measurements are computed. The dipole model results for the differential $b$-jet production cross section are compared to the recent ATLAS and CMS data while the results for $D$ and $B$ mesons production cross sections -- to the corresponding LHCb data. Several models for the phenomenological dipole cross section have been employed to estimate theoretical uncertainties of the dipole model predictions. We demonstrate that the primordial transverse momentum distribution of the projectile gluon significantly affects the meson spectra at low transverse momenta and contributes to the largest uncertainty of the dipole model predictions., Comment: 22 pages, 9 figures

Hadronic diffractive processes characterised by a hard scale (hard diffraction) contain a nontrivial interplay of hard and soft, nonperturbative interactions, which breaks down factorisation of short and long distances. On the contrary to the expectations based on the factorization hypothesis, assuming that hard diffraction is a higher twist, these processes should be classified as a leading twist. We overview various implications of this important observation for diffractive radiation of Abelian (Drell-Yan, gauge bosons, Higgs boson) and non-Abelian (heavy flavors) particles, as well as direct coalescence into the Higgs boson of the non-perturbative intrinsic heavy flavour component of the hadronic wave function., Comment: 17 pages, 13 figures; final version published in Int. J. Mod. Phys. E (Special Issue on "Modern Topics on Non-perturbative QCD: Theory and Experiment")

Production of heavy photons (Drell-Yan), gauge bosons, Higgs bosons, heavy flavors, which is treated within the QCD parton model as a result of hard parton-parton collision, can be considered as a bremsstrahlung process in the target rest frame. In this review, we discuss the basic features of the diffractive channels of these processes in the framework of color dipole approach. The main observation is a dramatic breakdown of diffractive QCD factorisation due to the interplay between soft and hard interactions, which dominates these processes. This observation is crucial for phenomenological studies of diffractive reactions in high-energy hadronic collisions., Comment: 29 pages, 16 figures; typos corrected; references added; minor corrections

We investigate the azimuthal anisotropy $v_2$ of particle production in nucleus-nucleus collisions in the maximum entropy approach. This necessitates two new phenomenological input parameters $\delta$ and $\lambda_2$ compared with integrated multiplicity distributions. The parameter $\delta$ describes the deformation of a flux tube and can be theoretically calculated in a bag model with a bag constant which depends on the density of surrounding flux tubes. The parameter $\lambda_2$ defines the anisotropy of the particle distribution in momentum space and can be connected to $\delta$ via the uncertainty relation. In this framework we compute the anisotropy $v_2$ as a function of centrality, transverse momentum and rapidity in qualitative agreement with LHC data., Comment: 15 pages, 4 figures

We consider single-diffractive (SD) Higgs production in association with heavy flavour in proton-proton collisions at the LHC. The main focus of our study is a reliable estimate of SD/inclusive ratio, not a precision computation of the cross sections. The calculations are performed within the framework of the phenomenological dipole approach, which includes by default the absorptive corrections, i.e. the gap survival effects at the amplitude level. The dominant mechanism is the diffractive production of heavy quarks, which radiate a Higgs boson (Higgsstrahlung). Although diffractive production of $t$-quarks is grossly suppressed as $1/m_t^2$, the large Higgs-top coupling compensates this smallness and the Higgsstrahlung by $t$-quarks becomes the dominant contribution at large Higgs boson transverse momenta. We computed the basic observables such as the transverse momentum and rapidity distributions of the diffractively produced Higgs boson in association with the bottom and top quark pair. Finally, we discuss a potential relevance of the diffractive Higgsstrahlung in comparison to the Higgsstrahlung off intrinsic heavy flavor at forward Higgs boson rapidities., Comment: 24 pages, 5 figures; a comparison with intrinsic heavy flavour contribution and an extra figure have been added; conclusions unchanged; to appear in PRD

Part 2 of "Project X: Accelerator Reference Design, Physics Opportunities, Broader Impacts". In this Part, we outline the particle-physics program that can be achieved with Project X, a staged superconducting linac for intensity-frontier particle physics. Topics include neutrino physics, kaon physics, muon physics, electric dipole moments, neutron-antineutron oscillations, new light particles, hadron structure, hadron spectroscopy, and lattice-QCD calculations. Part 1 is available as arXiv:1306.5022 [physics.acc-ph] and Part 3 is available as arXiv:1306.5024 [physics.acc-ph]., Comment: 209 pp. with many figures; prepared in part for the DPF Community Summer Study; v2 corrects typos (including one author surname), adds an author, and conforms with the version being printed; v3 includes two more chapter authors in full list at the top

We discuss single diffractive gauge bosons ($\gamma^*,\,W^{\pm},\,Z$) production in proton-proton collisions at different (LHC and RHIC) energies within the color dipole approach. The calculations are performed for gauge bosons produced at forward rapidities. The diffractive cross section is predicted as function of fractional momentum and invariant mass of the lepton pair. We found a dramatic breakdown of the diffractive QCD factorisation caused by an interplay of hard and soft interactions. Data from the CDF experiment on diffractive production of $W$ and $Z$ are well explained in a parameter free way., Comment: 28 pages, 10 figures; a clarification of absorptive corrections has been added, typos corrected; the published version

Single diffractive Drell-Yan reaction in hadron-hadron collisions is considered as an important source of information on the properties of soft QCD interactions. In particular, it provides an access to the dynamics of the QCD factorisation breaking due to the interplay between hard and soft interactions which leads to a nontrivial energy and scale dependence of the Drell-Yan observables. We study the process at forward rapidities in high energy proton-(anti)proton collisions in the color dipole approach. Predictions for the total and differential cross sections of the diffractive lepton pair production are given at different energies., Comment: 8 pages, 3 figures, talk given at the International Conference on the Structure and the Interactions of the Photon including the 19th International Workshop on Photon-Photon Collisions, 22-27 May 2011, Spa, Belgium

We propose a novel mechanism for the production of the Higgs boson in inclusive hadronic collisions, which utilizes the presence of heavy quarks in the proton wave function. In these inclusive reactions the Higgs boson acquires the momenta of both the heavy quark and antiquark and thus carries 80% or more of the projectile's momentum. We predict that the cross section ${d \sigma/d x_F}(p \bar p \to H X)$ for the inclusive production of the Standard Model Higgs coming from intrinsic bottom Fock states is of order 150 fb at LHC energies, peaking in the region of $x_F \sim 0.9$. Our estimates indicate that the corresponding cross section coming from gluon-gluon fusion at $x_F = 0.9$ is relatively negligible and therefore the peak from intrinsic bottom should be clearly visible for experiments with forward detection capabilities. The predicted cross section for the production of the Standard Model Higgs coming from intrinsic heavy quark Fock states in the proton is sufficiently large that detection at the Tevatron and the LHC may be possible., Comment: 23 pages, 5 figures

We propose a novel mechanism for exclusive diffractive Higgs production $pp \to p H p $ in which the Higgs boson carries a significant fraction of the projectile proton momentum. This mechanism will provide a clear experimental signal for Higgs production due to the small background in this kinematic region. The key assumption underlying our analysis is the presence of intrinsic heavy flavor components of the proton bound state, whose existence at high light-cone momentum fraction $x$ has growing experimental and theoretical support. We also discuss the implications of this picture for exclusive diffractive quarkonium and other channels., Comment: 30 pages, 5 figures

The observed J/psi suppression in Pb+Pb collisions shows a drop at those large values of the transverse energy E_T which arise from fluctuations. The validity of existing models for J/psi suppression can be extended into this domain of E_T by introducing an ad hoc factor proportional to E_T. We propose a formalism in which the influence of E_T fluctuations on the J/psi suppression can be calculated and discuss the conditions under which the ad hoc factor is obtained., Comment: 10 pages LaTeX, 2 postscript figures, revised version with several changes and additions

In high energy nuclear collisions, the Glauber model is commonly used to evaluate $J/\psi$ suppression due to inelastic interaction with colorless bound nucleons. This requires an effective value for the $J/\psi$-nucleon absorption cross section which is larger than theoretically expected. On the other hand, multiple nucleon-nucleon collisions mediated by color exchange interactions, excite their color degrees of freedom. We investigate the importance of this effect and conclude that the related corrections are important to explain the effective value extrapolated from experiment., Comment: 6 pages Latex, 1 postscript figure, uses moriond.sty (included), talk at the XXXVth Rencontres de Moriond on QCD and Hadronic Interactions, 18 -- 25 March 2000, Les Arcs, France

In high energy nuclear collisions, the conventional Glauber model is commonly used to evaluate the contribution to $J/\psi$ suppression originating from the inelastic interaction with colorless bound nucleons. This requires an effective value for the $J/\psi$-nucleon absorption cross section which is larger than theoretically expected. On the other hand, multiple nucleon-nucleon collisions mediated by color exchange interactions, excite their color degrees of freedom. We investigate the importance of this effect and find that these excited states provide a larger cross section for $J/\psi$ absorption. We conclude that the related corrections are important to explain the effective value extrapolated from experiment., Comment: 21 pages Latex, 8 postscript figures

The medium energy antiproton beam facility which is under discussion at GSI offers new opportunities to study the QCD of heavy flavours, nuclear structure and exotic mesons. We discuss these topics and briefly highlight other problems in charm production and proton structure., Comment: The talk given at the meeting "Perspectives of Hadron Physics", GSI, Darmshtadt, June 8, 1998

An upper limit on $n-\bar n$ oscillations can be obtained from the stability of matter. This relation has been worked out theoretically and together with data yields $\tau_{n\bar n} > (1 - 2)\times 10^8 sec$. A recent publication claims a different relation and finds a nuclear suppression of the $n\to\bar n$ oscillations which is two orders of magnitude weaker than the previous evaluations. Using the same approach we find, nevertheless, that the earlier estimates are correct and conclude that future experiments with free neutrons from reactors are capable to put a stronger limit on the $n - \bar n$ oscillation time than experiments with large amount of neutrons bound in nuclei., Comment: To be published in proc. of the Workshop on Future Directions in Quark Nuclear Physics, Adelaide, March 9 - 20, 1998

We compare a few types of high energy reactions which seem to be practical for polarimetry at RHIC. Coulomb-nuclear interference (CNI) in pp elastic scattering leads to a nearly energy-independent left-right asymmetry A_N(t) at small t. The systematical uncertainty of this method is evaluated to be ~ 10%. The CNI in proton-nucleus elastic scattering is predicted to result in larger values of A_N(t) and occurs at larger momentum transfer than in pp elastic scattering. This energy independent asymmetry can be used for the polarimetry. As an absolute polarimeter one can use elastic pp scattering on a fixed target at large |t| ~ 1 - 1.5 GeV^2, where A_N(t) is reasonably large and nearly energy independent. Although it cannot be reliably calculated, one can calibrate the polarimeter by measuring the polarisation of the recoil protons., Comment: 18 pages, 4 Postscript figures; Based on the talks presented by the author at the Workshop on Polarimetry at RHIC, RIKEN Research Center, BNL, July 20 - August 23, 1997

We consider deep-inelastic lepton scattering, Drell-Yan lepton pair and heavy quark production in the reference frame of the target. These reactions traditionally treated as hard have, however, a substantial leading twist soft contribution. One of the manifestations of such a soft component, nuclear shadowing, is overviewed., Comment: Latex 12 pages including 4 figures. Invited talk at the Workshop Hirschegg'95: Dynamical Properties of Hadrons in Nuclear Matter. In proceedings, ed. by H. Feldmeier and W. N\"orenberg, Darmstadt, 1995, p. 102

Our main observations are: (i) The effective path length of the $c\bar c$ wave packet, which is produced in the nucleus, grows with the energy of the produced charmonium. The variation is controlled by the coherence length $l_c=2E_{\Psi}/M^2_{\Psi}$. (ii) A colorless $c\bar c$ wave packet produced in $pp$-interaction is a specific linear combination of the $J/\Psi$ and $\Psi'$ states, and interacts substantially weaker that any of its components. The time evolution of this wave packet is controlled by the formation length, $l_f=2E_{\Psi}/(M^2_{\Psi'} - M^2_{\Psi})$. Exact formulas incorporating with these effects are derived. The interplay of the two phenomena results in a nontrivial energy- and $x_F$-dependence of the nuclear suppression of the charmonium production in proton-nucleus and nucleus-nucleus collisions and explains some of the experimentally observed effects., Comment: Latex 7 pages, 4 postscript files with figures. Invited talks presented by B. Kopeliovich at the XXXI st Rencontres de Moriond, ''QCD and High-Energy Hadronic Interactions'' March 23-30, 1996, Les Arcs, France and at PANIC'96, May 22-28, 1996, Williamsburg, USA Misprints in eqs. (13) and (14) are corrected

A new scaling variable is introduced in terms of which nuclear shadowing in deep-inelastic scattering is universal, i.e. independent of $A$, $Q^2$ and $x$. This variable can be interpreted as a measure of the number of gluons probed by the hadronic fluctuations of a virtual photon during their lifetime. According to recent data from the H1 and ZEUS experiments, the gluon density in a proton rises steeply as $x$ tends to zero. So nuclei which in the infinite momentum frame have a large surface density of gluons model at larger $x$ values what we expect for the proton at much smaller $x$. Using experimental information on nuclear shadowing we predict the unitarity corrections to the proton structure function at small $x$ and extract the bare Pomeron intercept., Comment: 9 pages, LATEX, 3 uuencoded figures

We calculate the nuclear suppression for $J/\Psi$ and $\Psi'$ production within a coupled channel approach in the subspace of the $J/\Psi$ and $\Psi'$ states. We are able to explain, why (i) the $J/\Psi$ and $\Psi'$ show the same suppression from $200\ GeV$ to $800\ GeV$ in proton-nucleus collisions and why (ii) the $\Psi'$ is absorbed more strongly than the $J/\Psi$ in nucleus-nucleus collisions at $200\ GeV$. The numerical result which includes only interactions with nucleons acconts for half of the observed suppression in sulphur-uranium collisions., Comment: 8 pages, LATEX, 3 uuencoded figures

Recently claimed \cite{dj1,dj2,FC} anomalous nuclear effects in di-jet production are analyzed in view of multiple interaction of projectile/ejectile partons in nuclear matter. We derive model--independent relations between A-dependence of the cross section and nuclear broadening of transverse momentum. Comparison with the data show that initial/final state interaction of partons participating in hard process is hard as well. This is a solid argument in favor of smallness of a color neutralization radius of a hadronizing highly virtual quark., Comment: 6 pages, Talk presented at the 5th Conference on the Intersection of Particle and Nuclear Physics, St. Petersburg, Florida, 1994

Diquark-antidiquark states are expected to exist as a natural complement of mesons and baryons. Although they were predicted long ago, and some candidates were found experimentally, none has, as yet, been reliably identified. We suggest that the search for the so-called $C(1480)$-meson in reactions such as photoproduction $\gamma N\rightarrow\phi\pi N$ and $K N \rightarrow \phi \pi \Lambda$ should provide a decisive way to settle this issue. Estimates of the cross sections are given using present experimental information on the C-meson and assuming its diquark-antidiquark structure. Sizable cross sections are predicted (of the order of 0.1 $\mu$b for photoproduction and of the order of 0.1 mb for $KN$ at the maximum with an insignificant background). Failure to find this kind of signal would imply that the C-meson is {\it not} a diquark-antidiquark state., Comment: 9 pages in LATex + 6 figs. (available from authers upon request), IUHET-269/93

Contrary to widespread opinion, color transparency (CT) brings essential ambiguity to, rather than helps in, study of the nuclear spectral function in quasielastic lepton scattering, $A(l,l'p)A'$, at high $Q^2$. Although the nuclear attenuation vanishes, the final state interaction (FSI) of a small-size ejectile wave packet, propagating through nuclear matter, remains. It manifests itself in a substantial, but uncertain, longitudinal momentum transfer to the nuclear medium. We predict a strong Fermi-momentum bias of the nuclear transparency at high $Q^2$, which enters as a factor at the nuclear spectral function, and makes uncertain the results of measuring the high-momentum tail of Fermi distribution., Comment: 8 pages, two figs. available upon request. Invited talk at the Workshop on electron-nucleus scattering, Marciana Marina, Elba, July 5-10, 1993

Color transparency (CT) is an effect of suppression of nuclear shadowing of hard reactions, closely related to the color screening. A brief review of theoretical development and experimental search for CT, failed and successful, are presented. A special emphasis is made on a quantum-mechanical nature of CT, as opposed to a wide spread erroneousclassical treatment of this phenomenon. The typical predictions of the classical approach, all contradicting quantum mechanics are: - factorization of cross section of hard reactions on a nucleus;\\ - "nuclear transparency", a normalized ratio of nuclear to nucleon cross sections, cannot exceed one;\\ - the larger is a radius of a hadron, the stronger it attenuates in a nucleus;\\ - the higher is the energy of hadrons participating in a hard reaction, the less is the nuclear attenuation;\\ - due to CT hard processes provide a better opportunity to study Fermi-momentum distribution, than soft reactions; etc. (Talk presented at XXVIII Rencontres de Moriond, March 1993), Comment: 9 pages + 5figs (available upon request), report DFTT 24/93

Nuclei are unique analyzers of the space-time development of jets at early stage. We argue that the gluon bremsstrahlung, rather than the color string, is the main mechanism of hadronization of highly virtual quarks produced in a hard interaction. It results in an energy- and time-independent density of energy loss, like a color string, but steeply dependent on the quark virtuality. Effects of formation zone (FZ) and color transparency (CT) substantially affect the jet quenching in a nuclear matter. The latter also plays an important role in the broadening of transverse momentum distribution of a quark passing a nucleus. Parameter-free calculations provide a good description of available data on nuclear effects in the leading hadron production in deep-inelastic lepton scattering, back-to-back high-$p_T$ hadron pair production, broadening of the transverse momentum distribution in the Drell-Yan process of lepton pair production on nuclei., Comment: 7 pages + 3 figs (available upon request), report# LPTHE 93-16

It is argued that color transparency in quasi elastic scattering of electrons and hadrons on nuclei is possible only due to Fermi-motion. We found a strong dependence of nuclear transparency on Bjorken x in (e,e'p), it is close to the Glauber model expectations at $x>1$, but increases and even exceeds one at $x<1$. It is argued that color transparency is accompanied by large longitudinal momentum transfer to nuclear matter during the passage of the small size wave packet. \vspace{\fill}, Comment: 10 pages + 2 fig. TRIUMF, TRI PP-92-95