73694775
Momentum space dipole amplitude for DIS and inclusive hadron production
We show how the AGBS model, originally developed for deep inelastic scattering applied to HERA data on the proton structure function, can also describe the RHIC data on single inclusive hadron yield for d + Au and p + p collisions through a new simultaneous fit. The single inclusive hadron production is modeled through the color glass condensate, which uses the quark(and gluon) condensate amplitudes in momentum space. The AGBS model is also a momentum space model based on the asymptotic solutions of the BK equation, although a different definition of the Fourier transform is used. This description entirely in transverse momentum of both processes arises for the first time. The small difference between the simultaneous fit and the one for HERA data alone suggests that the AGBS model describes very well both kind of processes and thus emerges as a good tool to investigate the inclusive hadron production data. We use this model for predictions at LHC energies, which agree quite well with available experiment...
73694775
Momentum space dipole amplitude for DIS and inclusive hadron production
We show how the AGBS model, originally developed for deep inelastic scattering applied to HERA data on the proton structure function, can also describe the RHIC data on single inclusive hadron yield for d + Au and p + p collisions through a new simultaneous fit. The single inclusive hadron production is modeled through the color glass condensate, which uses the quark(and gluon) condensate amplitudes in momentum space. The AGBS model is also a momentum space model based on the asymptotic solutions of the BK equation, although a different definition of the Fourier transform is used. This description entirely in transverse momentum of both processes arises for the first time. The small difference between the simultaneous fit and the one for HERA data alone suggests that the AGBS model describes very well both kind of processes and thus emerges as a good tool to investigate the inclusive hadron production data. We use this model for predictions at LHC energies, which agree quite well with available experiment...
4827292
Backward dilepton production in color dipole and parton models
The Drell-Yan dilepton production at backward rapidities is studied in proton-nucleus collisions at Relativistic Heavy Ion Collider and LHC energies by comparing two different approaches: the k{sub T} factorization at next-to-leading order with intrinsic transverse momentum and the same process formulated in the target rest frame, i.e., the color dipole approach. Our results are expressed in terms of the ratio between p(d)-A and p-p collisions as a function of transverse momentum and rapidity. Three nuclear parton distribution functions are used: EKS (Eskola, Kolhinen, and Ruuskanen), EPS08, and EPS09 and, in both approaches, dileptons show sensitivity to nuclear effects, specially regarding the intrinsic transverse momentum. Also, there is room to discriminate between formalisms: the color dipole approach lacks soft effects introduced by the intrinsic k{sub T}. Geometric scaling GBW (Golec-Biernat and Wusthoff) and BUW (Boer, Utermann, and Wessels) color dipole cross section models and also a DHJ (Dumitru, Hayashigaki, and Jalilian-Marian) model, which breaks geometric scaling, are used. No change in the ratio between collisions is observed, showing that this observable is not changed by the particular shape of the color dipole cross section. Furthermore, our k{sub T} factorization results are compared with color glass condensate results at forward rapidities: themore » results agree at Relativistic Heavy Ion Collider although disagree at LHC, mainly due to the different behavior of target gluon and quark shadowing.« less
122917905
DILEPTON PRODUCTION AT BACKWARD RAPIDITIES
34857484
Confronting color dipole and intrinsic kT approaches in D-Y dilepton production
We study the Drell-Yan dilepton production in proton-nucleus collisions at RHIC energies. We use two different approaches: the usual intrinsic transverse momentum approach at NLO in the infinitum momentum frame; and the color dipole in the target rest frame. We compare both formalisms at backward rapidities (proton as a target). At forward rapidities, we use earlier results considering the nucleus in a Color Glass Condensate phase. We show qualitative agreement between the two formalisms through the nuclear modification ratio as a function of both rapidity and transverse momentum and that low-mass dileptons are relevant observables to probe nuclear effects.
38260061
Dipole Scattering Amplitude in Momentum Space: Investigating Fluctuations at HERA
not included in the original Balitsky-JIMWLK hierarchy and obviously missed in its mean field version, the BK equation. The fluctuations have been exhaustively investigated in recent years and their effects in the high energy evolution will be discussed in the next sections of this contribution. What one can antecipate is that they dramatically influence the high energy scattering, at least in the case when the strong coupling constant as is fixed. Among these investigations, one can cite a recent study [6] of the possible implications of the gluon number fluctuations in the measurements of the F2 proton structure function of deep inelastic scattering (DIS) at HERA, through well known models for the dipole-proton cross section in coordinate space [7,8]. The results show that, although they may be present in the DIS measurements, they seem not to strongly influence the evolution at HERA energies. In these proceedings we use the first model for the dipoleproton cross section developed in momentum space [9] with fluctuation effects included to fit the last HERA data. This model has shown to be successful in the description of DIS data, specially with heavy quark (charm) contributions included, by using a mean-field (BK) inspired parametrization for the scattering amplitude, which enters in the expression for the dipole-proton cross section. Some preliminary results are presented and some future expectations on the effects of fluctuations at HERA are discussed.
32897419
Electromagnetic wave scattering by Schwarzschild black holes.
We analyze the scattering of a planar monochromatic electromagnetic wave incident upon a Schwarzschild black hole. We obtain accurate numerical results from the partial wave method for the electromagnetic scattering cross section and show that they are in excellent agreement with analytical approximations. The scattering of electromagnetic waves is compared with the scattering of scalar, spinor, and gravitational waves. We present a unified picture of the scattering of all massless fields for the first time.
121641075
Electromagnetic absorption cross section of Reissner-Nordström black holes revisited
The absorption cross section of Reissner-Nordstroem black holes for the electromagnetic field is computed numerically for arbitrary frequencies, taking into account the coupling of the electromagnetic and gravitational perturbations. We also compute the conversion coefficients of electromagnetic to gravitational waves by scattering from a Reissner-Nordstroem black hole.
124961099
Absorption of scalar waves by static black holes and analogues
121246958
Electromagnetic absorption cross section of Reissner-Nordström black holes
The absorption cross section of Reissner-Nordstroem black holes for the electromagnetic field is computed numerically for arbitrary frequencies. The numerical results are in excellent agreement with the low- and high-frequency limits, which are obtained with analytical methods. Special emphasis is given to the extreme Reissner-Nordstroem black hole case.
118367082
Scattering of massless scalar waves by Reissner-Nordström black holes
We present a study of scattering of massless planar scalar waves by a charged nonrotating black hole. Partial wave methods are applied to compute scattering and absorption cross sections, for a range of incident wavelengths. We compare our numerical results with semiclassical approximations from a geodesic analysis, and find excellent agreement. The glory in the backward direction is studied, and its properties are shown to be related to the properties of the photon orbit. The effects of the black hole charge upon scattering and absorption are examined in detail. As the charge of the black hole is increased, we find that the absorption cross section decreases, and the angular width of the interference fringes of the scattering cross section at large angles increases. In particular, the glory spot in the backward direction becomes wider. We interpret these effects under the light of our geodesic analysis.