Small Gluonic Spots in the Nucleon: Searching for Signatures in Data

Nuclear shadowing and color glass condensate are possible only at sufficiently small x where parton clouds of different nucleons overlap in the longitudinal direction. Another condition vital for these effect, an overlap of partons in impact parameters, is not easy to fulfill for gluons which are located within small spots, as follows from the observed weakness of diffractive gluon radiation (smallness of the triple-Pomeron coupling). The predicted weakness of the leading twist gluon shadowing has been confirmed recently by data for J/Psi production and Cronin effect in d-Au collisions at RHIC. Smallness of gluonic spots also leads to a rather low value of the slope of the Pomeron trajectory, confirmed by ZEUS data on elastic photoproduction of J/Psi. At the same time, saturation of unitarity for central pp collisions leads to a substantial increase of the Pomeron slope in good agreement with elastic pp data.Comment: Talk given by B. Povh at the Quark Matter 200

Proton Spin in Deep Inelastic Scattering

So far the analyses of the polarized structure functions of the proton and neutron have been limited to the evaluation of their integrals and comparing them to the prediction of the static quark model of the nucleon. We extended our analysis to the x dependence of the polarized structure functions and observe: the measured structure function excellently agrees with the prediction of the static quark model for Bjorken $x>0.2$ and drops rapidly for $x<0.2$. It is suggested that for Bjorken $x>0.2$ electrons get scattered on the undamaged constituent quarks (alias valence quarks) denoted as quasi-elastic scattering on the constituent quarks and for $x<0.2$ the constituent quarks fragment. In the fragmentation strong interaction is involved which does not preserve the polarization.Comment: 6 pages, 4 figures, Presented at the workshop on Diffraction and Low-x, Reggio Calabria, Aug. 26-Sept. 1, 201

Baryon Number Flow in High-Energy Collisions

It is not obvious which partons in the proton carry its baryon number (BN). We present arguments that BN is associated with a specific topology of gluonic fields, rather than with the valence quarks. The BN distribution is easily confused with the difference between the quark and antiquark distributions. We argue, however, that they have quite different x-dependences. The distribution of BN asymmetry distribution is nearly constant at small x while q(x)-\bar q(x) \propto \sqrt{x}. This constancy of BN produces energy independence of the \bar pp annihilation cross section at high energies. Recent measurement of the baryon asymmetry at small x at HERA confirms this expectation. The BN asymmetry at mid-rapidities in heavy ion collisions is substantially enhanced by multiple interactions, as has been observed in recent experiments at the SPS. The same gluonic mechanism of BN stopping increases the production rate for cascade hyperons in a good accord with data. We expect nearly the same as at SPS amount of BN stopped in higher energy collisions at RHIC and LHC, which is, however, spread ove larger rapidity intervals.Comment: The estimated baryon stopping at RHIC is corrected in the Summar

Baryon Asymmetry of the Proton Sea at Low xx

We predict a nonvanishing baryon asymmetry of the proton sea at low $x$. It is expected to be about $7\%$ and nearly $x$-independent at $x < 0.5 \times 10^{-3}$. The asymmetry arises from the baryon-antibaryon component of the Pomeron, rather than from the valence quarks of the proton, which are wide believed carriers of baryon number. Experimental study of $x$-distribution of the baryon asymmetry of the proton sea can be performed in $ep$ or $\gamma p$ interactions at HERA, where $x\sim 10^{-5}$ are reachable, smaller than at any of existing or planned proton colliders.Comment: 19 pages, LaTeX type, including 5 figure

Properties of a future susy universe

In the string landscape picture, the effective potential is characterized by an enormous number of local minima of which only a minuscule fraction are suitable for the evolution of life. In this "multiverse", random transitions are continually made between the various minima with the most likely transitions being to minima of lower vacuum energy. The inflationary era in the very early universe ended with such a transition to our current phase which is described by a broken supersymmetry and a small, positive vacuum energy. However, it is likely that an exactly supersymmetric (susy) phase of zero vacuum energy as in the original superstring theory also exists and that, at some time in the future, there will be a transition to this susy world. In this article we make some preliminary estimates of the consequences of such a transition.Comment: 17 pages, 3 figures; intermediate extensions/revisions available at http://www.bama.ua.edu/~lclavell/Susyria.pd