Excitation of Color Degrees of Freedom of Nuclear Matter and J/ψJ/\psi Suppression

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 figure

Charmonium Suppression in Heavy Ion Collisions by Prompt Gluons

In relativistic heavy ion collisions, also the bremsstrahlung of gluons in the fragmentation regions of the nuclei suppresses the produced charmonium states. In the energy range of the SPS, the radiation of semi-hard gluons occurs in the Bethe-Heitler regime and the density of gluons and therefore the suppression goes like $(AB)^{1\over3}$, where $A$ and $B$ are the nucleon numbers of the projectile and target nuclei. In contrast, the suppression via collisions with nucleons is proportional to $(A^{1\over3} + B^{1\over3})$. Parameter free perturbative QCD calculations are in a good agreement with the data on $J/\Psi$ and $\Psi'$ suppression in heavy ion collisions at SPS CERN. At higher energies (RHIC, LHC) the number of gluons which are able to break-up the charmonium substantially decreases and the additional suppression is expected to vanish.Comment: One figure is adde

Diffractive Higgs Production from Intrinsic Heavy Flavors in the Proton

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 figure

Higgs Hadroproduction at Large Feynman x

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 figure

Nuclear Shadowing in Electro-Weak Interactions

Shadowing is a quantum phenomenon leading to a non-additivity of electroweak cross sections on nucleons bound in a nucleus. It occurs due to destructive interference of amplitudes on different nucleons. Although the current experimental evidence for shadowing is dominated by charged-lepton nucleus scattering, studies of neutrino nucleus scattering have recently begun and revealed unexpected results.Comment: 77 pages, 57 figures. To be published in "Progress in Particle and Nuclear Physics" 201

The Relative J/ΨJ/\Psi to Ψ′\Psi' Suppression in Proton-Nucleus and Nucleus-Nucleus Collisions

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 figure

Scanning the Quark-Gluon Plasma with Charmonium

We suggest the variation of charmonium suppression with Feynman x_F in heavy ion collisions as a novel and sensitive probe for the properties of the matter created in such reactions. In contrast to the proton-nucleus case where nuclear suppression is weakest at small x_F, final state interactions with the comoving matter create a minimum at x_F=0, which is especially deep and narrow if a quark-gluon plasma is formed. While a particularly strong effect is predicted at SPS, at the higher RHIC energy it overlaps with the expected sharp variation with x_F of nuclear effects and needs comparison with proton-nucleus data. If thermal enhancement of J/\Psi production takes over at the energies of RHIC and LHC, it will form an easily identified peak, rather than dip in x_F dependence. We predict a steep dependence on centrality and suggest that this new probe is complementary to the dependence on transverse energy, and is more sensitive to a scenario of final state interactions.Comment: 5 pages including 3 figures. Stylistic and clarifying corrections are mad