arXiv
(422.153 recursos)
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Mostrando recursos 1 - 20 de 11.354
1.
Evidence for $B^+\to\omega l^+ \nu$ - Collaboration, The Belle
We have searched for the decay $B^+\to\omega l^+\nu$ ($l=e$ or $\mu$) in 78
fb$^{-1}$ of $\Upsilon(4S)$ data (85 million $B\bar B$ events) accumulated with
the Belle detector. The final state is fully reconstructed using the $\omega$
decay into $\pi^+\pi^-\pi^0$, combined with detector hermeticity to estimate
the neutrino momentum. A signal of $414\pm 125$ events is found in the data,
corresponding to a branching fraction of $(1.3\pm 0.4\pm 0.2\pm 0.3)\times
10^{-4}$, where the first two errors are statistical and systematic,
respectively. The third error reflects the estimated form-factor uncertainty.
2.
Evidence of B0 --> rho0 pi0 - Dragic, J.; Gershon, T.
We present the first evidence of the decay B0 --> rho0 pi0, using 140fb^-1 of
data collected at the Upsilon(4S) resonance with the Belle detector at the KEKB
asymmetric e+e- collider. We detect a signal with a significance of 3.5
standard deviations, and measure the branching fraction to be Br(B0 ->- rho0
pi0) = (5.1 +/- 1.6(stat) +/- 0.9(syst))*10^-6.
3.
A Determination of the CKM Parameter |Vus| - Alexopoulos, KTeV Collaboration: T.
We present a determination of the CKM parameter |Vus| based on new
measurements of the six largest KL branching fractions and semileptonic form
factors by the KTeV (E832) experiment at Fermilab. We find |Vus| = 0.2252 +-
0.0008(KTeV) +- 0.0021(ext), where the errors are from KTeV measurements and
from external sources. We also use the measured branching fractions to
determine the CP violation parameter |eta+-| = [2.228 +- 0.005(KTeV) +-
0.009(ext)]E-3.
4.
Direct CP Violating Asymmetry in B0 -> K+pi- Decays - Collaboration, BaBar; Aubert, B.
We present a measurement of the direct CP violating asymmetry in the decay B0
-> K+pi- using 227 x 10^6 Y(4S) -> BBbar decays collected with the BaBar
detector at the PEP-II asymmetric-energy e+e- collider at SLAC, we observe a
total signal yield of n(K-pi+) + n(K+pi-) = 1606 +- 51 decays and measure the
asymmetry [n(K-pi+)-n(K+pi-)]/[n(K-p+-)+n(K+pi-)] = -0.133+-0.030 (stat) +-
0.009 (syst). The probability of observing such an asymmetry in the absence of
direct CP violation is 1.3 x 10^-5, corresponding to 4.2 standard deviations.
5.
Search for CP violation in the decay B0->D*+-D-+ - Aushev, T.; Collaboration, for the Belle
We report a search for CP-violating asymmetry in B0 -> D*+- D-+ decays. The
analysis employs two methods of B0 reconstruction: full and partial. In the
full reconstruction method all daughter particles of the B0 are required to be
detected; the partial reconstruction technique requires a fully reconstructed
D- and only a slow pion from the D*+ -> D0 pi_slow+ decay. From a fit to the
distribution of the time interval corresponding to the distance between two B
meson decay points we calculate the CP-violating parameters and find the
significance of nonzero CP asymmetry to be 2.7 standard deviations.
6.
Determination of the e+e- -> gamma gamma (gamma) cross-section at LEP 2 - Abdallah, The DELPHI Collaboration: J.
A test of the benchmark QED process e+e- -> gamma gamma (gamma) is reported,
using the data collected with the DELPHI detector at LEP 2. The data analysed
were recorded at centre-of-mass energies ranging from 161 GeV to 208 GeV and
correspond to a total integrated luminosity of 656.4 pb^{-1}. The Born
cross-section for the process e+e- -> gamma gamma (gamma) was determined,
confirming the validity of QED at the highest energies ever attained in
electron-positron collisions. Lower limits on the parameters of a number of
possible deviations from QED, predicted within theoretical frameworks
expressing physics beyond the Standard Model, were derived.
7.
Resonances in $J/\psi \to \phi \pi ^+\pi ^-$ and $\phi K^+K^-$ - Ablikim, M.
A partial wave analysis is presented of $J/\psi \to \phi \pi ^+\pi ^-$ and
$\phi K^+K^-$ from a sample of 58M $J/\psi$ events in the BES II detector. The
$f_0(980)$ is observed clearly in both sets of data, and parameters of the
Flatt\' e formula are determined accurately: $M = 965 \pm 8$ (stat) $\pm 6$
(syst) MeV/c$^2$, $g_1 = 165 \pm 10 \pm 15 $ MeV/c$^2$, $g_2/g_1 = 4.21 \pm
0.25 \pm 0.21$. The $\phi \pi \pi$ data also exhibit a strong $\pi \pi$ peak
centred at $M = 1335$ MeV/c$^2$. It may be fitted with $f_2(1270)$ and a
dominant $0^+$ signal made from $f_0(1370)$ interfering...
8.
Semileptonic D Decays from CLEO and BELLE - Gao, Yongsheng
Recent semileptonic D meson decay results are summarized, including the
improved measurements of absolute branching fractions for exclusive D0
semileptonic decays into $K^{-}e^{+}\nu$, $\pi^{-}e^{+}\nu$ and
$K^{*-}e^{+}\nu$, and the first observation and absolute branching fraction
measurement of $D^{0} \to \rho^{-}e^{+}\nu$ with the first CLEO-c data sample.
9.
Status and Perspectives of Neutrino Physics - Bettini, Alessandro
I will first give a brief but comprehensive review of the status of our
knowledge in neutrino physics. With reference to a not too far future I will
then discuss the perspectives that appear to me to be most important and
promising.
10.
CP violation in b->c anti-c d decays at Belle - Aushev, T.
We report a measurement of the CP violation parameters in b->c anti-c d
decays. Mixing-induced CP violation involving this transition is studied using
a sample of B0->J/psi pi0, D*+D*- and D*+-D-+ decays with a data set
accumulated at the Upsilon(4S) resonance with the Belle detector at the KEKB
energy-asymmetric e+e- collider. CP violation parameters are extracted from a
fit to the distributions of time intervals between two B0 meson decay vertexes.
11.
Upper limit on the eta -> pi+pi- branching ratio with the KLOE experiment - collaboration, KLOE
We have searched with the KLOE detector for the P and CP violating decay eta
-> pi^+pi^- in a sample of 1.55 x 10^7 eta's from the decay phi -> eta gamma of
phi mesons produced in e+e- annihilations at DAFNE. No signal is found. We
obtain the upper limit BR(eta -> pi^+pi^-) < 1.3 x 10^-5 at 90% confidence
level.
12.
Study of the decay mode D^0 -> K-K+pi-pi+ - Link, the FOCUS Collaboration: J.
Using data from the FOCUS (E831) experiment at Fermilab, we present a new
measurement of the branching ratio for the Cabibbo-favored decay mode $D^0 \to
K^-K^+\pi^-\pi^+$. From a sample of $2669 \pm 101$ fully reconstructed $D^0 \to
K^-K^+\pi^-\pi^+$ events, we measure $\Gamma(D^0 \to
K^-K^+\pi^-\pi^+)/\Gamma(D^0 \to K^-\pi^-\pi^+\pi^+) = 0.0295 \pm 0.0011(stat.)
\pm 0.0008(syst.)$.
A coherent amplitude analysis has been performed to determine the resonant
substructure of this decay mode. This analysis reveals a dominant contribution
from $D^0 \to K_1^+ K-$ modes.
13.
QCD'04: Recent Results from Belle - Seuster, R.
The huge data sample accumulated at the KEKB storage ring allows for
dedicated analyses in charm spectroscopy. A new, narrow resonance with a mass
of 3.872\GeV was found in decays of $B$ mesons. Its properties remain
unexplained. Results on various properties of the \DsJ resonances have been
updated. Older results on the unexpectedly large cross section for double
charmonium production in \epem annihilation have been confirmed and a refined
analysis is presented.
14.
Searches and electroweak measurements at HERA - Caron, Sascha
The H1 and ZEUS collaborations have used the HERA I data to search for
physics beyond the SM and to test electroweak physics in electron-proton
collisions. The new period of data taking (HERA II) has started and first HERA
II analyses become available. An overview is given of recent highlights,
including isolated lepton and multi-lepton events, tests of models of new
physics and the first systematic search for deviations in all final states with
high transverse momentum.
15.
Evidence for muon neutrino oscillation in an accelerator-based experiment - Aliu, K2K Collaboration: E.
We present results for muon neutrino oscillation in the KEK to Kamioka (K2K)
long-baseline neutrino oscillation experiment. K2K uses an accelerator-produced
muon neutrino beam with a mean energy of 1.3 GeV directed at the
Super-Kamiokande detector. We observed the energy dependent disappearance of
muon neutrino, which we presume have oscillated to tau neutrino. The
probability that we would observe these results if there is no neutrino
oscillation is 0.0050% (4.0 sigma).
16.
The phase of the sigma -> pi-pi amplitude in J/Psi -> omega-pi-pi - Bugg, D. V.
The phase variation of the sigma -> pi-pi amplitude is accurately determined
as a function of mass from BES II data for J/Psi -> omega-pi-pi. The
determination arises from interference with the strong b1(1235)-pi amplitude.
The observed phase variation agrees within errors with that in pi-pi elastic
scattering.
17.
Determination of the CKM Matrix Element |V_cb| from Semileptonic B Decays - Luth, Vera G.
We report studies of semileptonic decays, B --> X_c l nu, based on a sample
of 88 million BB events recorded with the BABAR detector. We have measured four
moments of the electron energy distribution and four moments of the hadronic
mass distribution, each as a function of the minimum electron energy. From
these moments we determine the inclusive branching fraction, the CKM matrix
element |V_cb|, and other heavy quark parameters, using Heavy Quark Expansions
(HQE) to order 1/m_b^3 in the kinetic mass scheme. In addition, we have studied
a large sample of exclusive B^0 --> D^*- l^+ nu decays. This sample is used to
extract the vector...
18.
Neutral Higgs Boson Search at Tevatron - Yao, Wei-Ming
We review searches for neutral Higgs Boson performed by the CDF and D0
collaborations using approximately 200 pb$^{-1}$ of the dataset accumulated
from $p\bar p$ collisions at the center-of-mass energy of 1.96 TeV. No signals
are found and limits on the Standard Model (SM) Higgs or SM-like Higgs
production cross section times branching ratio and couplings of the Higgs boson
in MSSM are presented, including the future prospects of discovery Higgs at the
end of Run II.
19.
Measurements of B meson decays to omega K* and omega rho - Collaboration, The BABAR; Aubert, B.
We describe searches for B meson decays to the charmless vector-vector final
states omega K* and omega rho in 89 million B-Bbar pairs produced in e+e-
annihilation at sqrt(s)=10.58 GeV. We measure the following branching fractions
in units of 10^{-6}:
BF(B0 -> omega K*0) = 3.4 +1.8 -1.6 +/- 0.4 (<6.0),
BF(B+ -> omega K*+) = 3.5 +2.5 -2.0 +/- 0.7 (<7.4),
BF(B0 -> omega rho0) = 0.6 +1.3 -1.1 +/- 0.4 (<3.3), and BF(B+ -> omega rho+)
= 12.6 +3.7 -3.3 +/- 1.6. The first error quoted is statistical, the second
systematic, and the upper limits are defined at 90% confidence level. For B+...
20.
A search for the decay $B^+ \to K^+ \nu \bar{\nu}$ - Aubert, B.; Collaboration, BABAR
We search for the rare flavor-changing neutral-current decay $B^+ \to K^+ \nu
\bar{\nu}$ in a data sample of 82 fb$^{-1}$ collected with the {\sl BABAR}
detector at the PEP-II B-factory. Signal events are selected by examining the
properties of the system recoiling against either a reconstructed hadronic or
semileptonic charged-B decay. Using these two independent samples we obtain a
combined limit of ${\mathcal B}(B^+ \to K^+ \nu \bar{\nu})<5.2 \times 10^{-5}$
at the 90% confidence level. In addition, by selecting for pions rather than
kaons, we obtain a limit of ${\mathcal B}(B^+ \to \pi^+ \nu \bar{\nu})<1.0
\times 10^{-4}$ using only the hadronic B reconstruction method.
1.
