334 research outputs found
A Study in Depth of f0(1370)
Claims have been made that f0(1370) does not exist. The five primary sets of
data requiring its existence are refitted. Major dispersive effects due to the
opening of the 4pi threshold are included for the first time; the sigma -> 4pi
amplitude plays a strong role. Crystal Barrel data on pbar-p -> 3pizero at rest
require f0(1370) signals of at least 32 and 33 standard deviations in 1S0 and
3P1 annihilation respectively. Furthermore, they agree within 5 MeV for mass
and width. Data on pbar-p -> eta-eta-pizero agree and require at least a 19
standard deviation contribution. This alone is sufficient to demonstrate the
existence of f0(1370). BES II data for J/Psi -> phi-pi-pi contain a visible
f0(1370) signal > 8 standard devations. In all cases, a resonant phase
variation is required. The possibility of a second pole in the sigma amplitude
due to the opening of the 4pi channel is excluded. Cern-Munich data for pi-pi
elastic scattering are fitted well with the inclusion of some mixing between
sigma, f0(1370) and f0(1500). The pi-pi widths for f2(1565), rho3(1690),
rho3(1990) and f4(2040) are determined.Comment: 25 pages, 22 figures. Typos corrected in Eqs 2 and 7. Introduction
rewritten. Conclusions unchange
Partial wave analysiss of pbar-p -> piminus-piplus, pizero-pizero, eta-eta and eta-etaprime
A partial wave analysis is presented of Crystal Barrel data on pbar-p ->
pizero-pizero, eta-eta and eta-etaprime from 600 to 1940 MeV/c, combined with
earlier data on d\sigma /d\Omega and P for pbar-p->piminus-piplus. The
following s-channel I=0 resonances are identified: (i) J^{PC} = 5^{--} with
mass and width (M,\Gamma) at (2295+-30,235^{+65}_{-40}) MeV, (ii) J^{PC} =
4^{++} at (2020+-12, 170+-15) MeV and (2300+-25, 270+-50) MeV, (iii) 3D3 JPC =
3^{--} at (1960+-15, 150+-25) MeV and (2210+-4$, 360+-55) MeV, and a 3G3 state
at (2300 ^{+50}_{-80}, 340+-150) MeV, (iv) JPC = 2^{++} at (1910+-30, 260+-40)
MeV, (2020+-30, 275+-35) MeV, (2230+-30, 245+-45) MeV, and (2300+-35, 290+-50)
MeV, (v) JPC = 1^{--} at (2005+-40, 275+-75) MeV, and (2165+-40, 160
^{+140}_{-70}) MeV, and (vi) JPC = 0^{++} at (2005+-30, 305+-50) MeV,
(2105+-15, 200+-25) MeV, and (2320+-30, 175+-45) MeV. In addition, there is a
less well defined 6^{++} resonance at 2485+-40 MeV, with Gamma = 410+-90 MeV.
For every JP, almost all these resonances lie on well defined linear
trajectories of mass squared v. excitation number. The slope is 1.10+-0.03
Gev^2 per excitation. The f_0(2105) has strong coupling to eta-\eta, but much
weaker coupling to pizero-pizero. Its flavour mixing angle between q-qbar and
s-sbar is (59-71.6)deg, i.e. dominant decays to s-sbar. Such decays and its
strong production in pbar-p interactions strongly suggest exotic character.Comment: Makes available the combined fit to Crystal Barrel data on pbar-p ->
2-body final states. 29 pages, 11 figures. Typo corrected in version
Precision Pion-Proton Elastic Differential Cross Sections at Energies Spanning the Delta Resonance
A precision measurement of absolute pi+p and pi-p elastic differential cross
sections at incident pion laboratory kinetic energies from T_pi= 141.15 to
267.3 MeV is described. Data were obtained detecting the scattered pion and
recoil proton in coincidence at 12 laboratory pion angles from 55 to 155
degrees for pi+p, and six angles from 60 to 155 degrees for pi-p. Single arm
measurements were also obtained for pi+p energies up to 218.1 MeV, with the
scattered pi+ detected at six angles from 20 to 70 degrees. A flat-walled,
super-cooled liquid hydrogen target as well as solid CH2 targets were used. The
data are characterized by small uncertainties, ~1-2% statistical and ~1-1.5%
normalization. The reliability of the cross section results was ensured by
carrying out the measurements under a variety of experimental conditions to
identify and quantify the sources of instrumental uncertainty. Our lowest and
highest energy data are consistent with overlapping results from TRIUMF and
LAMPF. In general, the Virginia Polytechnic Institute SM95 partial wave
analysis solution describes our data well, but the older Karlsruhe-Helsinki PWA
solution KH80 does not.Comment: 39 pages, 22 figures (some with quality reduced to satisfy ArXiv
requirements. Contact M.M. Pavan for originals). Submitted to Physical Review
Implications of unitarity and analyticity for the D\pi form factors
We consider the vector and scalar form factors of the charm-changing current
responsible for the semileptonic decay D\rightarrow \pi l \nu. Using as input
dispersion relations and unitarity for the moments of suitable heavy-light
correlators evaluated with Operator Product Expansions, including O(\alpha_s^2)
terms in perturbative QCD, we constrain the shape parameters of the form
factors and find exclusion regions for zeros on the real axis and in the
complex plane. For the scalar form factor, a low energy theorem and phase
information on the unitarity cut are also implemented to further constrain the
shape parameters. We finally propose new analytic expressions for the
form factors, derive constraints on the relevant coefficients from unitarity
and analyticity, and briefly discuss the usefulness of the new parametrizations
for describing semileptonic data.Comment: 10 pages, 7 figures, uses EPJ style files: expanded version of v1
with extended discussion, additional analysis, explanation, figure and
references; corresponds to EPJA versio
Measurement of the B0-anti-B0-Oscillation Frequency with Inclusive Dilepton Events
The - oscillation frequency has been measured with a sample of
23 million \B\bar B pairs collected with the BABAR detector at the PEP-II
asymmetric B Factory at SLAC. In this sample, we select events in which both B
mesons decay semileptonically and use the charge of the leptons to identify the
flavor of each B meson. A simultaneous fit to the decay time difference
distributions for opposite- and same-sign dilepton events gives ps.Comment: 7 pages, 1 figure, submitted to Physical Review Letter
Determination of the Form Factors for the Decay B0 --> D*-l+nu_l and of the CKM Matrix Element |Vcb|
We present a combined measurement of the Cabibbo-Kobayashi-Maskawa matrix element and of the parameters , , and , which fully characterize the form factors of the decay in the framework of HQET, based on a sample of about 52,800 decays recorded by the BABAR detector. The kinematical information of the fully reconstructed decay is used to extract the following values for the parameters (where the first errors are statistical and the second systematic): , , , . By combining these measurements with the previous BABAR measurements of the form factors which employs a different technique on a partial sample of the data, we improve the statistical accuracy of the measurement, obtaining: and Using the lattice calculations for the axial form factor , we extract , where the third error is due to the uncertainty in
Study of the Exclusive Initial-State Radiation Production of the System
A study of exclusive production of the system through initial-state r adiation is performed in a search for charmonium states, where or . The mesons are reconstructed in the , , and decay modes. The is reconstructed through the decay mode. The analysis makes use of an integrated luminosity of 288.5 fb collected by the BaBar experiment. The mass spectrum shows a clear signal. Further structures appear in the 3.9 and 4.1 GeV/ regions. No evidence is found for Y(4260) decays to , implying an up per limit \frac{\BR(Y(4260)\to D \bar D)}{\BR(Y(4260)\to J/\psi \pi^+ \pi^-)} < 7.6 (95 % confidence level)
A search for the decay
We search for the rare flavor-changing neutral-current decay in a data sample of 82 fb 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
at the 90% confidence level. In addition, by selecting for pions rather than
kaons, we obtain a limit of using only the hadronic B reconstruction method.Comment: 7 pages, 8 postscript figures, submitted to Phys. Rev. Let
High-reflectivity broadband distributed Bragg reflector lattice matched to ZnTe
We report on the realization of a high quality distributed Bragg reflector
with both high and low refractive index layers lattice matched to ZnTe. Our
structure is grown by molecular beam epitaxy and is based on binary compounds
only. The high refractive index layer is made of ZnTe, while the low index
material is made of a short period triple superlattice containing MgSe, MgTe,
and ZnTe. The high refractive index step of Delta_n=0.5 in the structure
results in a broad stopband and the reflectivity coefficient exceeding 99% for
only 15 Bragg pairs.Comment: 4 pages, 3 figure
Measurement of the CP-Violating Asymmetry Amplitude sin2
We present results on time-dependent CP-violating asymmetries in neutral B decays to several CP eigenstates. The measurements use a data sample of about 88 million Y(4S) --> B Bbar decays collected between 1999 and 2002 with the BABAR detector at the PEP-II asymmetric-energy B Factory at SLAC. We study events in which one neutral B meson is fully reconstructed in a final state containing a charmonium meson and the other B meson is determined to be either a B0 or B0bar from its decay products. The amplitude of the CP-violating asymmetry, which in the Standard Model is proportional to sin2beta, is derived from the decay-time distributions in such events. We measure sin2beta = 0.741 +/- 0.067 (stat) +/- 0.033 (syst) and |lambda| = 0.948 +/- 0.051 (stat) +/- 0.017 (syst). The magnitude of lambda is consistent with unity, in agreement with the Standard Model expectation of no direct CP violation in these modes
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