6,185 research outputs found
Measurement of the Atmospheric Muon Charge Ratio at TeV Energies with MINOS
The 5.4 kton MINOS far detector has been taking charge-separated cosmic ray
muon data since the beginning of August, 2003 at a depth of 2070
meters-water-equivalent in the Soudan Underground Laboratory, Minnesota, USA.
The data with both forward and reversed magnetic field running configurations
were combined to minimize systematic errors in the determination of the
underground muon charge ratio. When averaged, two independent analyses find the
charge ratio underground to be 1.374 +/- 0.004 (stat.) +0.012 -0.010(sys.).
Using the map of the Soudan rock overburden, the muon momenta as measured
underground were projected to the corresponding values at the surface in the
energy range 1-7 TeV. Within this range of energies at the surface, the MINOS
data are consistent with the charge ratio being energy independent at the two
standard deviation level. When the MINOS results are compared with measurements
at lower energies, a clear rise in the charge ratio in the energy range 0.3 --
1.0 TeV is apparent. A qualitative model shows that the rise is consistent with
an increasing contribution of kaon decays to the muon charge ratio.Comment: 16 pages, 17 figure
Measurement of neutrino velocity with the MINOS detectors and NuMI neutrino beam
The velocity of a ~3 GeV neutrino beam is measured by comparing detection times at the near and far detectors of the MINOS experiment, separated by 734 km. A total of 473 far detector neutrino events was used to measure (v-c)/c=5.12.910-5 (at 68% C.L.). By correlating the measured energies of 258 charged-current neutrino events to their arrival times at the far detector, a limit is imposed on the neutrino mass of mnu<50 MeV/c2 (99% C.L.)
Measurement of the Branching Fraction for B- --> D0 K*-
We present a measurement of the branching fraction for the decay B- --> D0
K*- using a sample of approximately 86 million BBbar pairs collected by the
BaBar detector from e+e- collisions near the Y(4S) resonance. The D0 is
detected through its decays to K- pi+, K- pi+ pi0 and K- pi+ pi- pi+, and the
K*- through its decay to K0S pi-. We measure the branching fraction to be
B.F.(B- --> D0 K*-)= (6.3 +/- 0.7(stat.) +/- 0.5(syst.)) x 10^{-4}.Comment: 7 pages, 1 postscript figure, submitted to Phys. Rev. D (Rapid
Communications
A Study of Time-Dependent CP-Violating Asymmetries and Flavor Oscillations in Neutral B Decays at the Upsilon(4S)
We present a measurement of time-dependent CP-violating asymmetries in
neutral B meson decays collected with the BABAR detector at the PEP-II
asymmetric-energy B Factory at the Stanford Linear Accelerator Center. The data
sample consists of 29.7 recorded at the
resonance and 3.9 off-resonance. One of the neutral B mesons,
which are produced in pairs at the , is fully reconstructed in
the CP decay modes , , , () and , or in flavor-eigenstate
modes involving and (). The flavor of the other neutral B meson is tagged at the time of
its decay, mainly with the charge of identified leptons and kaons. The proper
time elapsed between the decays is determined by measuring the distance between
the decay vertices. A maximum-likelihood fit to this flavor eigenstate sample
finds . The value of the asymmetry amplitude is determined from
a simultaneous maximum-likelihood fit to the time-difference distribution of
the flavor-eigenstate sample and about 642 tagged decays in the
CP-eigenstate modes. We find , demonstrating that CP violation exists in the neutral B meson
system. (abridged)Comment: 58 pages, 35 figures, submitted to Physical Review
Study of e+e- --> pi+ pi- pi0 process using initial state radiation with BABAR
The process e+e- --> pi+ pi- pi0 gamma has been studied at a center-of-mass
energy near the Y(4S) resonance using a 89.3 fb-1 data sample collected with
the BaBar detector at the PEP-II collider. From the measured 3pi mass spectrum
we have obtained the products of branching fractions for the omega and phi
mesons, B(omega --> e+e-)B(omega --> 3pi)=(6.70 +/- 0.06 +/- 0.27)10-5 and
B(phi --> e+e-)B(phi --> 3pi)=(4.30 +/- 0.08 +/- 0.21)10-5, and evaluated the
e+e- --> pi+ pi- pi0 cross section for the e+e- center-of-mass energy range
1.05 to 3.00 GeV. About 900 e+e- --> J/psi gamma --> pi+ pi- pi0 gamma events
have been selected and the branching fraction B(J/psi --> pi+ pi- pi0)=(2.18
+/- 0.19)% has been measured.Comment: 21 pages, 37 postscript figues, submitted to Phys. Rev.
Evidence for the Rare Decay B -> K*ll and Measurement of the B -> Kll Branching Fraction
We present evidence for the flavor-changing neutral current decay and a measurement of the branching fraction for the related
process , where is either an or
pair. These decays are highly suppressed in the Standard Model,
and they are sensitive to contributions from new particles in the intermediate
state. The data sample comprises
decays collected with the Babar detector at the PEP-II storage ring.
Averaging over isospin and lepton flavor, we obtain the branching
fractions and , where the
uncertainties are statistical and systematic, respectively. The significance of
the signal is over , while for it is .Comment: 7 pages, 2 postscript figues, submitted to Phys. Rev. Let
Measurement of Branching Fraction and Dalitz Distribution for B0->D(*)+/- K0 pi-/+ Decays
We present measurements of the branching fractions for the three-body decays
B0 -> D(*)-/+ K0 pi^+/-B0 -> D(*)-/+ K*+/- using
a sample of approximately 88 million BBbar pairs collected by the BABAR
detector at the PEP-II asymmetric energy storage ring.
We measure:
B(B0->D-/+ K0 pi+/-)=(4.9 +/- 0.7(stat) +/- 0.5 (syst)) 10^{-4}
B(B0->D*-/+ K0 pi+/-)=(3.0 +/- 0.7(stat) +/- 0.3 (syst)) 10^{-4}
B(B0->D-/+ K*+/-)=(4.6 +/- 0.6(stat) +/- 0.5 (syst)) 10^{-4}
B(B0->D*-/+ K*+/-)=(3.2 +/- 0.6(stat) +/- 0.3 (syst)) 10^{-4}
From these measurements we determine the fractions of resonant events to be :
f(B0-> D-/+ K*+/-) = 0.63 +/- 0.08(stat) +/- 0.04(syst) f(B0-> D*-/+ K*+/-) =
0.72 +/- 0.14(stat) +/- 0.05(syst)Comment: 7 pages, 3 figures submitted to Phys. Rev. Let
Measurement of the B+ --> p pbar K+ Branching Fraction and Study of the Decay Dynamics
With a sample of 232x10^6 Upsilon(4S) --> BBbar events collected with the
BaBar detector, we study the decay B+ --> p pbar K+ excluding charmonium decays
to ppbar. We measure a branching fraction Br(B+ --> p pbar
K+)=(6.7+/-0.5+/-0.4)x10^{-6}. An enhancement at low ppbar mass is observed and
the Dalitz plot asymmetry suggests dominance of the penguin amplitude in this B
decay. We search for a pentaquark candidate Theta*++ decaying into pK+ in the
mass range 1.43 to 2.00 GeV/c2 and set limits on Br(B+ -->
Theta*++pbar)xBr(Theta*++ --> pK+) at the 10^{-7} level.Comment: 8 pages, 7 postscript figures, submitted to Phys. Rev. D (Rapid
Communications
Search for the W-exchange decays B0 --> Ds(*)- Ds(*)+
We report a search for the decays , , in a sample of 232
million decays to \BBb ~pairs collected with the \babar detector
at the PEP-II asymmetric-energy storage ring. We find no significant
signal and set upper bounds for the branching fractions: and at 90% confidence level.Comment: 8 pages, 2 figures, submitted to PRD-R
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