20 research outputs found
Hadronic Contributions to the Photon Vacuum Polarization and their Role in Precision Physics
I review recent evaluations of the hadronic contribution to the shift in the
fine structure constant and to the anomalous magnetic moment of the muon.
Substantial progress in a precise determination of these important observables
is a consequence of substantially improved total cross section measurement by
the CMD-2 and BES II collaborations and an improved theoretical understanding.
Prospects for further possible progress is discussed.Comment: 17 pages 7 figures 2 tables, update: incl. CMD-2 data, reference
Closed-flavor pi + J/psi and pi + Upsilon Cross Sections at Low Energies from Dipion Decays
The scale of low energy c-cbar and b-bbar cross sections on light hadrons is
of great importance to searches for the quark gluon plasma using the
heavy-quarkonium suppression signature. Unfortunately, little is known about
these near-threshold cross sections at present, and recent theoretical
estimates span many orders of magnitude. Here we use experimental data on the
four observed closed-flavor heavy quarkonium hadronic decays psi' -> pi pi
J/psi, Upsilon' -> pi pi Upsilon, Upsilon'' -> pi pi Upsilon and Upsilon'' ->
pi pi Upsilon', combined with simple models of the transition amplitudes, to
estimate the pion scattering cross sections of c-cbar and b-bbar mesons near
threshold. Specifically we consider the closed-flavor reactions pi J/psi -> pi
psi', pi Upsilon -> pi Upsilon', pi Upsilon -> pi Upsilon'' and pi Upsilon' ->
pi Upsilon'' and their time-reversed analogues. Our results may be useful in
constraining theoretical models of the strong interactions of heavy quarkonia,
and can be systematically improved through future detailed studies of dipion
decays, notably psi' -> pi pi J/psi and Upsilon'' -> pi pi Upsilon.Comment: 6 pages, 6 figure
Fast computation of observed cross section for decays
It has been conjectured that the relative phase between strong and
electromagnetic amplitudes is universally in charmonium decays.
decaying into pseudoscalar pair provides a possibility to test
this conjecture. However, the experimentally observed cross section for such a
process is depicted by the two-fold integral which takes into account the
initial state radiative (ISR) correction and energy spread effect. Using the
generalized linear regression approach, a complex energy-dependent factor is
approximated by a linear function of energy. Taking advantage of this
simplification, the integration of ISR correction can be performed and an
analytical expression with accuracy at the level of 1% is obtained. Then, the
original two-fold integral is simplified into a one-fold integral, which
reduces the total computing time by two orders of magnitude. Such a simplified
expression for the observed cross section usually plays an indispensable role
in the optimization of scan data taking, the determination of systematic
uncertainty, and the analysis of data correlation.Comment: 8 pages, 5 figure
Quark-hadron-duality in the charmonium and upsilon system
In this work we discuss the practical and conceptual issues related to
quark-hadron-duality in heavy-heavy systems. Recent measurements in the
charmonium region allow a direct test of quark-hadron-duality. We present a
formula for non-resonant background production in e^+ e^- \to D{\bar D} and
extract the resonance parameters of the \psi(3S)-\psi(6S). The obtained results
are used to investigate the upsilon energy range.Comment: 21 pages, 3 figures, references adde
Experimental studies of e + e -→ some charmless processes containing K S0 at √s = 3.773 and 3.65 GeV
We measure the observed cross sections for the charmless processes e + e -→K S0 K - K - K + π ++ c.c., K S0 K - π + η+c.c., K S0 K - π + π + π - η+c.c., K S0 K - K - K + π + η+c.c., K S0 K - K - K + π + π 0+c.c., K S0 K - ρ ++c.c. and K S0 K - π + ρ 0+c.c. We also extract upper limits on the branching fractions for ψ(3770) decays into these final states at 90% C.L. Analyzed data samples correspond to 17.3 pb-1 and 6.5 pb-1 integrated luminosities registered, respectively, at √s = 3.773 and 3.65 GeV, with the BES-II detector at the BEPC collider. © 2009 Springer-Verlag / Società Italiana di Fisica.published_or_final_versionSpringer Open Choice, 21 Feb 201
Recommended from our members
Psi(2S) two- and three-body hadronic decays
Phys.Rev.D67:052002,2003 We report measurements of branching fractions for psi(2S) decays into omega
pi pi, b1 pi,omega f2(1270),omega KK, omega p pbar, phi pi pi, phi f0(980),phi
KK, and an upper limit for phi p pbar final states based on a data sample of 4
X 10^6 psi(2S) events collected with the BESI detector at the Beijing
Electron-Positron Collider. The branching fractions for b1 pi and omega
f2(1270) update previous BES results, while those for other decay modes are
first measurements. The ratios of psi(2S)and J/psi branching fractions are
smaller than what is expected from the 12% rule by a factor of five for omega
f2(1270),by a factor of two for omega pi pi, omega p pbar, and phi KK, while
for other studied channels the ratios are consistent with expectation within
errors