476 research outputs found
Charm and Bottom Quark Masses from Perturbative QCD
Using a new result for the first moment of the hadronic production cross
section at order , and new data on the and
resonances for the charm quark, we determine the \msb masses of the
charm and bottom quarks to be GeV and
GeV. We assume that the continuum
contribution to the sum rules is adequately described by pQCD. While we observe
a large reduction of the perturbative error, the shifts induced by the
theoretical input are very small. The main change in the central value of
is related to the experimental data. On the other hand, the value of is
not changed by our calculation to the assumed precision.Comment: 5 pages, 2 figures, final version as publishe
The heavy quark's self energy from moving NRQCD on the lattice
We present a calculation of the heavy quark's self energy in moving NRQCD to
one-loop in perturbation theory. Results for the energy shift and external
momentum renormalisation are discussed and compared with non-perturbative
results. We show that the momentum renormalisation is small, which is the
result of a remnant of re-parameterisation invariance on the lattice.Comment: Talk given at Lattice2004(heavy), Fermilab, June 21-26, 200
Exercise Intensity and Energy Expenditure of a Simulated-sport Exergame versus Real-world Sport
Despite the multitude of local and national health initiatives aimed at increasing physical activity levels in the United States, there remains a dire need to aid individuals and families in adopting regular physical activity regimens. This lack of activity necessitates the use of novel and innovative methods for encouraging regular physical activity, such as the use of simulated-sport exergames. However, it is unclear whether these games can generate comparable physiological states of exercise to those seen within the actual sports they are simulating. Using data taken from a larger study, the purpose of the current study was to objectively compare physiological measures of exercise intensity and energy expenditure for a simulated-sport exergame versus its respective real-world sport, using the sport of racquetball. Undergraduate students (n = 103) who did not regularly exercise were provided with twice weekly, 30-minute training sessions for a new sport (racquetball) and were randomized into three different conditions of introductory training (None, Exergame, and Traditional Training) over an eight week period. This introductory training took place during Weeks 1 – 4, then all groups were transitioned into playing the actual sport of racquetball. The exergame group required participants to play a racquetball exergame for introductory training, while the traditional training group played the sport of racquetball on a racquetball court. The third group served as a control and came to introductory training sessions at the university activity center, but was only required to read or study. All participants were fitted with accelerometers during participation in order to measure levels of activity (via accelerometer counts), exercise intensity, steps taken and calories burned. As expected, analyses revealed that the traditional training group showed greater levels of all outcomes than all other groups during Weeks 1-4. Contrary to expectations, the exergame group did not show greater activity levels or energy expenditure than the control group at any time. All groups showed similar levels of activity once transitioned into playing actual racquetball. These findings support previous literature suggesting that an actual sport can produce significantly greater activity levels than its exergame counterpart. These results also provide evidence that exergames produce levels of activity that fall well below those suggested by ACSM minimum exercise guidelines. Future interventions should use these results by limiting the use of exergames to the introductory phase of training
Charm as a domain wall fermion in quenched lattice QCD
We report a study describing the charm quark by a domain-wall fermion (DWF)
in lattice quantum chromodynamics (QCD). Our study uses a quenched gauge
ensemble with the DBW2 rectangle-improved gauge action at a lattice cutoff of
GeV. We calculate masses of heavy-light (charmed) and
heavy-heavy (charmonium) mesons with spin-parity and ,
leptonic decay constants of the charmed pseudoscalar mesons ( and ),
and the - mixing parameter. The charm quark mass is found to be
GeV. The mass splittings in
charmed-meson parity partners and are
degenerate within statistical errors, in accord with experiment, and they
satisfy a relation , also consistent with
experiment. A C-odd axial vector charmonium state, \chi_{c1}m_{h_{c}} = 3533(11)_{\rm stat.}\chi_{c1}) mass. However, in this regard, we emphasize
significant discrepancies in the calculation of hyperfine splittings on the
lattice. The leptonic decay constants of and mesons are found to be
MeV and
,
where the first error is statistical, the second a systematic due to chiral
extrapolation and the third error combination of other known systematics. The
- mixing bag parameter, which enters the
transition amplitude, is found to be .Comment: 49 pages, 15 figure
as a tetraquark state with QCD sum rules in heavy quark limit
In this article, we take the point of view that the charmed scalar meson
be a tetraquark state and devote to calculate its mass within
the framework of the QCD sum rules approach in the heavy quark limit. The
numerical values for the mass of the are consistent with the
experimental data, there must be some tetraquark component in the scalar meson
. Detailed discussions about the threshold parameter and Borel
parameter for the multiquark states are also presented.Comment: 9 pages, 1 figure, third versio
Excited B mesons from the lattice
We determine the energies of the excited states of a heavy-light meson
, with a static heavy quark and light quark with mass approximately
that of the strange quark from both quenched lattices and with dynamical
fermions. We are able to explore the energies of orbital excitations up to L=3,
the spin-orbit splitting up to L=2 and the first radial excitation. These mesons will be very narrow if their mass is less than 5775 MeV -- the
threshold. We investigate this in detail and present evidence that the
scalar meson (L=1) will be very narrow and that as many as 6
excited states will have energies close to the threshold and should also
be relatively narrow.Comment: 17 pages, 6 ps figure
Heavy-Quark Symmetry and the Electromagnetic Decays of Excited Charmed Strange Mesons
Heavy-hadron chiral perturbation theory (HHPT) is applied to the decays
of the even-parity charmed strange mesons, D_{s0}(2317) and D_{s1}(2460).
Heavy-quark spin symmetry predicts the branching fractions for the three
electromagnetic decays of these states to the ground states D_s and D_s^* in
terms of a single parameter. The resulting predictions for two of the branching
fractions are significantly higher than current upper limits from the CLEO
experiment. Leading corrections to the branching ratios from chiral loop
diagrams and spin-symmetry violating operators in the HHPT Lagrangian can
naturally account for this discrepancy. Finally the proposal that the
D_{s0}(2317) (D_{s1}(2460)) is a hadronic bound state of a D (D^*) meson and a
kaon is considered. Leading order predictions for electromagnetic branching
ratios in this molecular scenario are in very poor agreement with existing
data.Comment: 25 pages, 3 figure
Excited Charmed Mesons: Observations, Analyses and Puzzles
We review the status of recently observed positive parity charmed resonances,
both in the non-strange and in the strange sector. We describe the experimental
findings, the main theoretical analyses and the open problems deserving further
investigations.Comment: LaTeX, 25 pages, 5 figures. Invited revie
An estimate of the flavour singlet contributions to the hyperfine splitting in charmonium
We explore the splitting between flavour singlet and non-singlet mesons in
charmonium. This has implications for the hyperfine splitting in charmonium
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