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Register a new user$D$ - meson production at very forward rapidities: estimating the intrinsic charm contribution
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We study $D$ - meson production at forward rapidities taking into account the non - linear effects in the QCD dynamics and the intrinsic charm component of the proton wave function. The total cross section, the rapidity distributions and the Feynman - $x$ distributions are calculated for $p p$ collisions at different center of mass energies. Our results show that, at the LHC, the intrinsic charm component changes the $D$ rapidity distributions in a region which is beyond the coverage of the LHCb detectors. At higher energies the IC component dominates the $y$ and $x_F$ distributions exactly in the range where the produced $D$ mesons decay and contribute the most to the prompt atmospheric neutrino flux measured by the ICECUBE Collaboration. We compute the $x_F$ - distributions and demonstrate that they are enhanced at LHC energies by approximately one order of magnitude in the $0.2 le x_F le 0.8$ range.
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The complete understanding of the basic constituents of hadrons and the hadronic dynamics at high energies are two of the main challenges for the theory of strong interactions. In particular, the existence of intrinsic heavy quark components in the hadron wave function must be confirmed (or disproved). In this paper we propose a new mechanism for the production of $D$-mesons at forward rapidities based on the Color Glass Condensate (CGC) formalism and demonstrate that the resulting transverse momentum spectra are strongly dependent on the behavior of the charm distribution at large Bjorken $x$. Our results show clearly that the hypothesis of intrinsic charm can be tested in $pp$ and $p(d) A$ collisions at RHIC and LHC.
Using the dipole picture for electron-nucleus deep inelastic scattering at small Bjorken $x$, we study the effects of gluon saturation in the nuclear target on the cross-section for SIDIS (single inclusive hadron, or jet, production). We argue that the sensitivity of this process to gluon saturation can be enhanced by tagging on a hadron (or jet) which carries a large fraction $z simeq 1$ of the longitudinal momentum of the virtual photon. This opens the possibility to study gluon saturation in relatively hard processes, where the virtuality $Q^2$ is (much) larger than the target saturation momentum $Q_s^2$, but such that $z(1-z)Q^2lesssim Q_s^2$. Working in the limit $z(1-z)Q^2ll Q_s^2$, we predict new phenomena which would signal saturation in the SIDIS cross-section. For sufficiently low transverse momenta $k_perpll Q_s$ of the produced particle, the dominant contribution comes from elastic scattering in the black disk limit, which exposes the unintegrated quark distribution in the virtual photon. For larger momenta $k_perpgtrsim Q_s$, inelastic collisions take the leading role. They explore gluon saturation via multiple scattering, leading to a Gaussian distribution in $k_perp$ centred around $Q_s$. When $z(1-z)Q^2ll Q^2$, this results in a Cronin peak in the nuclear modification factor (the $R_{pA}$ ratio) at moderate values of $x$. With decreasing $x$, this peak is washed out by the high-energy evolution and replaced by nuclear suppression ($R_{pA}<1$) up to large momenta $k_perpgg Q_s$. Still for $z(1-z)Q^2ll Q_s^2$, we also compute SIDIS cross-sections integrated over $k_perp$. We find that both elastic and inelastic scattering are controlled by the black disk limit, so they yield similar contributions, of zeroth order in the QCD coupling.
We propose a new experiment Relativistic Heavy Ion Collider forward (RHICf) for the precise measurements of very forward particle production at RHIC. The proposal is to install the LHCf Arm2 detector in the North side of the ZDC installation slot at the PHENIX interaction point. By installing high-resolution electromagnetic calorimeters at this location we can measure the spectra of photons, neutrons and pi0 at pseudorapidity eta>6.
In this paper, we propose an experiment for the precise measurements of very forward particle production at RHIC. The proposal is to install a LHCf-like calorimeter in the ZDC installation slot at one of the RHIC interaction points. By installing a high-resolution electromagnetic calorimeter at this location we measure the spectra of photons, neutrons and pi0 at pseudo rapidity eta above 6. The new measurements at 500 GeV p-p collisions contribute to improve the hadronic interaction models used in the cosmic-ray air shower simulations. Using a similar kinematic coverage at RHIC to that of the measurements at LHC, we can test the Feynman scaling with a wide energy range and make the extrapolation of models into cosmic-ray energy more reliable. Combination of a high position resolution of the LHCf detector and a high energy resolution of the ZDC makes it possible to determine pT of forward neutrons with the ever best resolution. This enables us to study the forward neutron spin asymmetry discovered at RHIC in more detail. Another new experiment expected at RHIC is world-first light-ion collisions. Cosmic-ray interaction models have been so far tested with accelerator data, but colliders have provided only p-p and heavy-ion collisions. To simulate the interaction between cosmic-ray particles and atmosphere, collision of light ions like nitrogen is a ultimate goal for the cosmic-ray physics. We propose 200 GeV p-N collisions together with 200 GeV p-p collisions to study the nuclear effects in the forward particle production. The experiment can be performed by using the existing LHCf detector. Considering the geometry and response of one of the LHCf detectors, we propose some short dedicated operations. Ideal beam conditions are summarized in this paper. Our basic idea is to bring one of the LHCf detectors to RHIC and then operate from 2016 season at RHIC.
In the spirit of Mueller-Navelet dijet production, we propose and study the inclusive production of a forward $J/psi$ and a very backward jet at the LHC as an observable to reveal high-energy resummation effects `a la BFKL. We obtain several predictions, which are based on the various mechanisms discussed in the literature to describe the production of the $J/psi$, namely, NRQCD singlet and octet contributions, and the color evaporation model.
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