Search results for "charm"
showing 10 items of 390 documents
Resonances in QCD
2015
We report on the EMMI Rapid Reaction Task Force meeting 'Resonances in QCD', which took place at GSI October 12-14, 2015. A group of 26 people met to discuss the physics of resonances in QCD. The aim of the meeting was defined by the following three key questions: What is needed to understand the physics of resonances in QCD? Where does QCD lead us to expect resonances with exotic quantum numbers? What experimental efforts are required to arrive at a coherent picture? For light mesons and baryons only those with ${\it up}$, ${\it down}$ and ${\it strange}$ quark content were considered. For heavy-light and heavy-heavy meson systems, those with ${\it charm}$ quarks were the focus. This docum…
Measurement of upsilon production in 7 TeV pp collisions at ATLAS
2013
Artículo escrito por un elevado número de autores, solo se referencian el que aparece en primer lugar, el nombre del grupo de colaboración, si le hubiere, y los autores pertenecientes a la UAM
Characterization of the atmospheric muon flux in IceCube
2015
Muons produced in atmospheric cosmic ray showers account for the by far dominant part of the event yield in large-volume underground particle detectors. The IceCube detector, with an instrumented volume of about a cubic kilometer, has the potential to conduct unique investigations on atmospheric muons by exploiting the large collection area and the possibility to track particles over a long distance. Through detailed reconstruction of energy deposition along the tracks, the characteristics of muon bundles can be quantified, and individual particles of exceptionally high energy identified. The data can then be used to constrain the cosmic ray primary flux and the contribution to atmospheric …
Production of muons from heavy-flavour hadron decays at high transverse momentum in Pb–Pb collisions atsNN=5.02and 2.76 TeV
2021
Abstract Measurements of the production of muons from heavy-flavour hadron decays in Pb–Pb collisions at s NN = 5.02 and 2.76 TeV using the ALICE detector at the LHC are reported. The nuclear modification factor R AA at s NN = 5.02 TeV is measured at forward rapidity ( 2.5 y 4 ) as a function of transverse momentum p T in central, semi-central, and peripheral collisions over a wide p T interval, 3 p T 20 GeV/c, in which muons from beauty-hadron decays are expected to take over from charm as the dominant source at high p T ( p T > 7 GeV/c). The R AA shows an increase of the suppression of the yields of muons from heavy-flavour hadron decays with increasing centrality. A suppression by a fact…
Charm and bottom quark masses from QCD moment sum rules
2002
In this work the charm and bottom quark masses are determined from QCD moment sum rules for the charmonium and upsilon systems. In our analysis we include both the results from non-relativistic QCD and perturbation theory at next-next-to-leading order. For the pole masses we obtain $M_c=1.75\pm 0.15$ GeV and $M_b=4.98\pm 0.125$ GeV. Using the potential-subtracted mass in intermediate steps of the calculation the MS-masses are determined to $m_c(m_c) = 1.19 \pm 0.11$ GeV and $m_b(m_b) = 4.24 \pm 0.10$ GeV.
Charmed pair correlations in π−Cu interactions at 230 GeV/c
1993
Abstract In the CERN NA32 experiment a high-resolution silicon vertex detector and a purely topological approach were used to collect 557 events consistent with associated charm production, both decay vertices being observed. The pseudorapidity gap distribution appears to be nearly independent of the nature of the charmed hadrons. This distribution is reasonably consistent with the next-to-leading order QCD calculations. However the azimuthal-angle distribution is significantly broader than the above predictions.
Charm quark mass determined from a pair of sum rules
2016
In this paper, we present preliminary results of the determination of the charm quark mass $\hat{m}_c$ from QCD sum rules of moments of the vector current correlator calculated in perturbative QCD at ${\cal O} (\hat \alpha_s^3)$. Self-consistency between two different sum rules allow to determine the continuum contribution to the moments without requiring experimental input, except for the charm resonances below the continuum threshold. The existing experimental data from the continuum region is used, then, to confront the theoretical determination and reassess the theoretic uncertainty.
Inclusive D* Production in Photon-Photon Collisions at Next-to-Leading Order QCD
2001
The next-to-leading order cross section for the inclusive production of charm quarks in gamma-gamma collisions is calculated as a function of the transverse momentum pT and the rapidity y in approaches using massive or massless charm quarks. For the direct cross section we derive the massless limit from the massive theory with the result that this limit differs from the massless version with MSbar factorization by finite corrections. Subtracting or adding these corrections allows us to compare the two approaches on equal footing. We establish massless and massive versions with 3 and 4 initial flavours which are shown to approach the massless approximations very fast with increasing pT. With…
Elliptic Flow of Electrons from Beauty-Hadron Decays in Pb-Pb Collisions at sNN=5.02 TeV
2021
The elliptic flow of electrons from beauty hadron decays at midrapidity ($|y|$ $<$ 0.8) is measured in Pb-Pb collisions at $\sqrt{s_{\rm NN}}$ = 5.02 TeV with the ALICE detector at the LHC. The azimuthal distribution of the particles produced in the collisions can be parameterized with a Fourier expansion, in which the second harmonic coefficient represents the elliptic flow, $v_{\rm 2}$. The $v_{\rm 2}$ coefficient is measured for the first time in transverse momentum ($p_{\rm{T}}$) range 1.3-6 GeV/$c$ in the centrality class 30-50%. The measurement of electrons from beauty-hadron decays exploits their larger mean proper decay length $c\tau \approx$ 500 $\mu$m compared to that of charm had…
QCD moment sum rules for Coulomb systems: the charm and bottom quark masses
2002
In this work the charm and bottom quark masses are determined from QCD moment sum rules for the charmonium and upsilon systems. To illustrate the special character of these sum rules when applied to Coulomb systems we first set up and study the behaviour of the sum rules in quantum mechanics. In our analysis we include both the results from nonrelativistic QCD and perturbation theory at next-next-to-leading order. The moments are evaluated at different values of q^2 which correspond to different relative influence among the theoretical contributions. In the numerical analysis we obtain the masses by choosing central values for all input parameters. The error is estimated from a variation of…