1,495 research outputs found
Sensor Scheduling for Optimal Observability Using Estimation Entropy
We consider sensor scheduling as the optimal observability problem for
partially observable Markov decision processes (POMDP). This model fits to the
cases where a Markov process is observed by a single sensor which needs to be
dynamically adjusted or by a set of sensors which are selected one at a time in
a way that maximizes the information acquisition from the process. Similar to
conventional POMDP problems, in this model the control action is based on all
past measurements; however here this action is not for the control of state
process, which is autonomous, but it is for influencing the measurement of that
process. This POMDP is a controlled version of the hidden Markov process, and
we show that its optimal observability problem can be formulated as an average
cost Markov decision process (MDP) scheduling problem. In this problem, a
policy is a rule for selecting sensors or adjusting the measuring device based
on the measurement history. Given a policy, we can evaluate the estimation
entropy for the joint state-measurement processes which inversely measures the
observability of state process for that policy. Considering estimation entropy
as the cost of a policy, we show that the problem of finding optimal policy is
equivalent to an average cost MDP scheduling problem where the cost function is
the entropy function over the belief space. This allows the application of the
policy iteration algorithm for finding the policy achieving minimum estimation
entropy, thus optimum observability.Comment: 5 pages, submitted to 2007 IEEE PerCom/PerSeNS conferenc
Semi-inclusive photon-hadron production in pp and pA collisions at RHIC and LHC
We investigate semi-inclusive photon-hadron production in the color glass
condensate (CGC) framework at RHIC and the LHC energies in proton-proton (pp)
and proton-nucleus (pA) collisions. We calculate the coincidence probability
for azimuthal correlation of pairs of photon-hadron and show that the away-side
correlations have a double-peak or a single-peak structure depending on trigger
particle selection and kinematics. This novel feature is unique for
semi-inclusive photon-hadron production compared to a similar measurement for
double inclusive dihadron production in pA collisions. We obtain necessary
conditions between kinematics variables for the appearance of a double-peak or
a single peak structure for the away-side photon-hadron correlations in pp and
pA collisions at forward rapidities and show that this feature is mainly
controlled by the ratio p_T^hadron/p_T^photon. Decorrelation of away-side
photon-hadron production by increasing the energy, rapidity and density, and
appearance of double-peak structure can be understood by QCD saturation
physics. We also provide predictions for the ratio of single inclusive prompt
photon to hadron production, and two-dimensional nuclear modification factor
for the semi-inclusive photon-hadron pair production at RHIC and the LHC at
forward rapidities.Comment: 16 pages, 20 figures; v2: latex Compilation problem in Figs. 3,4
correcte
Gluon saturation effects at forward rapidities at LHC in pp collisions
We investigate hadrons and direct photon production in pp collisions at the
LHC energy within the color-dipole approach. We show that greatest sensitivity
to gluon saturation effects is reached at very forward rapidities in pp
collisions at LHC (\sqrt{s}=14 TeV). The discrepancies among various saturation
models (fitted to HERA data) results can be about a factor of 2-3 at forward
rapidities. We found that the ratio of direct-photon to pion production can be
about 20-10 at forward rapidities \eta=7-8. Therefore, direct photon production
at forward rapidities should provide a rather clean probe as the background
from radiative hadronic decays is significantly suppressed.Comment: 4 pages, 6 figures, Contributed to "Lepton-Photon 2009 (LP09)",
Hamburg, German
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