24 research outputs found
Parton model versus color dipole formulation of the Drell-Yan process
In the kinematical region where the center of mass energy is much larger than
all other scales, the Drell-Yan process can be formulated in the target rest
frame in terms of the same color dipole cross section as low Bjorken-x deep
inelastic scattering. Since the mechanisms for heavy dilepton production appear
very different in the dipole approach and in the conventional parton model, one
may wonder whether these two formulations really represent the same physics. We
perform a comparison of numerical calculations in the color dipole approach
with calculations in the next-to-leading order parton model. For proton-proton
scattering, the results are very similar at low x_2 from fixed target to RHIC
energies, confirming the close connection between these two very different
approaches. We also compare the transverse momentum distributions of Drell-Yan
dileptons predicted in both formulations. The range of applicability of the
dipole formulation and the impact of future Drell-Yan data from RHIC for
determining the color dipole cross section are discussed. A detailed derivation
of the dipole formulation of the Drell-Yan process is also included.Comment: 20 pages, 5 figure
Conformal collider physics: Energy and charge correlations
We study observables in a conformal field theory which are very closely
related to the ones used to describe hadronic events at colliders. We focus on
the correlation functions of the energies deposited on calorimeters placed at a
large distance from the collision. We consider initial states produced by an
operator insertion and we study some general properties of the energy
correlation functions for conformal field theories. We argue that the small
angle singularities of energy correlation functions are controlled by the twist
of non-local light-ray operators with a definite spin. We relate the charge two
point function to a particular moment of the parton distribution functions
appearing in deep inelastic scattering. The one point energy correlation
functions are characterized by a few numbers. For superconformal
theories the one point function for states created by the R-current or the
stress tensor are determined by the two parameters and characterizing
the conformal anomaly. Demanding that the measured energies are positive we get
bounds on . We also give a prescription for computing the energy and
charge correlation functions in theories that have a gravity dual. The
prescription amounts to probing the falling string state as it crosses the
horizon with gravitational shock waves. In the leading, two derivative,
gravity approximation the energy is uniformly distributed on the sphere at
infinity, with no fluctuations. We compute the stringy corrections and we show
that they lead to small, non-gaussian, fluctuations in the energy distribution.
Corrections to the one point functions or antenna patterns are related to
higher derivative corrections in the bulk.Comment: 73 pages, 8 figures; v2: minor changes and added references; v3: more
references adde
Journey to DOR: a retro science-fiction story on researching eprescribing
The core of this paper is a science fiction short story. We are on planet DOR. A group of scientists are working on an experiment, changing underlying mechanisms of transmissions of a colossus machine – a complex system of gears and levers, wires and pipes. Some of its mechanisms are also known as D for Doctors, F for Pharmacists, P for Patients. Observers travel from Earth to study the experiment. Their dilemmas are unaided by their advanced research tools. The story is inspired by research carried out for the evaluation of the forthcoming Electronic Prescription Service in England (UK). Our fiction is fiction, but it is also a methodological means, a reflexive lever to elaborate and explore our research texts and to question the feasibility, meaning and impact of researching future technology