2,486 research outputs found
The logarithmic contribution to the QCD static energy at NNNNLO
Using pNRQCD and known results for the field strength correlator, we
calculate the ultrasoft contribution to the QCD static energy of a
quark-antiquark pair at short distances at NNNNLO in alpha_s. At the same
order, this provides the logarithmic terms of the singlet static potential in
pNRQCD and the log alpha_s terms of the static energy.Comment: 16 pages, 5 figures. Minor modifications. References added. Journal
versio
Overview of charmonium decays and production from Non-Relativistic QCD
I briefly review Non-Relativistic QCD and related effective theories, and
discuss applications to heavy quarkonium decay, and production in
electron-positron colliders.Comment: 8 pages, Invited talk at Charm 2010, Oct. 21-24, IHEP, Beijin
The QCD static energy at NNNLL
We compute the static energy of QCD at short distances at
next-to-next-to-next-to leading-logarithmic accuracy in terms of the three-loop
singlet potential. By comparing our results with lattice data we extract the
value of the unknown piece of the three-loop singlet potential.Comment: 25 pages, 16 figures. v2: Incorrect files for figure 7 replaced by
the correct ones. One reference adde
Extraction of alpha_s from radiative Upsilon(1S) decays
We improve on a recent determination of alpha_s from Gamma(Upsilon(1S)-->X
gamma)/Gamma(Upsilon(1S)-->X) with CLEO data by taking into account color octet
contributions and avoiding any model dependence in the extraction. We obtain
alpha_s(M_Upsilon(1S))= 0.184+0.015-0.014, which corresponds to
alpha_s(M_Z)=0.119+0.006-0.005.Comment: 11 pages. v2: One reference added. v3: Minor modification in an error
estimate. Journal versio
How to compute the thermal quarkonium spectral function from first principles?
In the limit of a high temperature T and a large quark-mass M, implying a
small gauge coupling g, the heavy quark contribution to the spectral function
of the electromagnetic current can be computed systematically in the
weak-coupling expansion. We argue that the scale hierarchy relevant for
addressing the disappearance ("melting") of the resonance peak from the
spectral function reads M >> T > g^2 M > gT >> g^4 M, and review how the heavy
scales can be integrated out one-by-one, to construct a set of effective field
theories describing the low-energy dynamics. The parametric behaviour of the
melting temperature in the weak-coupling limit is specified.Comment: 8 pages; to appear in the Proceedings of SEWM08, Amsterdam, the
Netherlands, August 26-29, 200
A first estimate of triply heavy baryon masses from the pNRQCD perturbative static potential
Within pNRQCD we compute the masses of spin-averaged triply heavy baryons
using the now-available NNLO pNRQCD potentials and three-body variational
approach. We focus in particular on the role of the purely three-body
interaction in perturbation theory. This we find to be reasonably small and of
the order 25 MeV Our prediction for the Omega_ccc baryon mass is 4900(250) in
keeping with other approaches. We propose to search for this hitherto
unobserved state at B factories by examining the end point of the recoil
spectrum against triple charm.Comment: 18 figures, 21 page
Spectroscopy, leptonic decays and the nature of heavy quarkonia
We examine the electronic width ratios of Upsilon resonances below the BBbar
threshold by means of an effective (Cornell-type) QCD potential incorporating
1/m_b corrections obtained from a prior fit to the bottomonium spectrum. From
our analysis we conclude that the Upsilon(2S) and Upsilon(3S) states should
belong to the strong-coupling (nonperturbative) regime while the Upsilon(1S)
state should belong to the weak-coupling (perturbative) regime, in agreement
with a previous study based on radiative decays.Comment: 8 page
Systematic study of the PDC speckle structure for quantum imaging applications
Sub shot noise imaging of weak object by exploiting Parametric Down Converted
light represents a very interesting technological development. A precise
characterization of PDC speckle structure in dependence of pump beam parameters
is a fundamental tool for this application. In this paper we present a first
set of data addressed to this purpose
EXP-Crowd: A Gamified Crowdsourcing Framework for Explainability
The spread of AI and black-box machine learning models made it necessary to explain their behavior. Consequently, the research field of Explainable AI was born. The main objective of an Explainable AI system is to be understood by a human as the final beneficiary of the model. In our research, we frame the explainability problem from the crowds point of view and engage both users and AI researchers through a gamified crowdsourcing framework. We research whether it's possible to improve the crowds understanding of black-box models and the quality of the crowdsourced content by engaging users in a set of gamified activities through a gamified crowdsourcing framework named EXP-Crowd. While users engage in such activities, AI researchers organize and share AI- and explainability-related knowledge to educate users. We present the preliminary design of a game with a purpose (G.W.A.P.) to collect features describing real-world entities which can be used for explainability purposes. Future works will concretise and improve the current design of the framework to cover specific explainability-related needs
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