812 research outputs found
Fermilab E791
Fermilab E791, a very high statistics charm particle experiment, recently
completed its data taking at Fermilab's Tagged Photon Laboratory. Over 20
billion events were recorded through a loose transverse energy trigger and
written to 8mm tape in the the 1991-92 fixed target run at Fermilab. This
unprecedented data sample containing charm is being analysed on many-thousand
MIP RISC computing farms set up at sites in the collaboration. A glimpse of the
data taking and analysis effort is presented. We also show some preliminary
results for common charm decay modes. Our present analysis indicates a very
rich yield of over 200K reconstructed charm decays.Comment: 4 pages, 1 figure, LaTe
The TeV spectrum of H1426+428
The BL Lac object H1426+428 was recently detected as a high energy gamma-ray
source by the VERITAS collaboration (Horan et al. 2002). We have reanalyzed the
2001 portion of the data used in the detection in order to examine the spectrum
of H1426+428 above 250 GeV. We find that the time-averaged spectrum agrees with
a power law of the shape dF/dE = 10^(-7.31 +- 0.15(stat) +- 0.16(syst)) x
E^(-3.50 +- 0.35(stat) +- 0.05(syst)) m^(-2)s^(-1)TeV^(-1) The statistical
evidence from our data for emission above 2.5 TeV is 2.6 sigma. With 95% c.l.,
the integral flux of H1426+428 above 2.5 TeV is larger than 3% of the
corresponding flux from the Crab Nebula. The spectrum is consistent with the
(non-contemporaneous) measurement by Aharonian et al. (2002) both in shape and
in normalization. Below 800 GeV, the data clearly favours a spectrum steeper
than that of any other TeV Blazar observed so far indicating a difference in
the processes involved either at the source or in the intervening space.Comment: LaTeX, 8 pages, 4 figures, accepted for publication in Ap
Search for the Flavor-Changing Neutral-Current Decays and
We report the results of a search for the flavor-changing neutral-current
decays and in
data from Fermilab charm hadroproduction experiment E791. No signal above
background is found, and we obtain upper limits on branching fractions,
and
, at the 90\% confidence
level.Comment: nine pages with figures; compressed, uuencoded postscrip
Measurement of the Ds Lifetime
We report the results of a precise measurement of the Ds meson lifetime based
on 1662 +/- 56 fully reconstructed Ds -> phi pi decays, from the charm
hadroproduction experiment E791 at Fermilab. Using an unbinned maximum
likelihood fit, we measure the Ds lifetime to be 0.518 +/- 0.014 +/- 0.007 ps.
The ratio of the measured Ds lifetime to the world average D0 lifetime is 1.25
+/- 0.04. This result differs from unity by six standard deviations, indicating
significantly different lifetimes for the Ds and the D0.Comment: 12 pages, 3 figures, 2 table. LaTe
Study of the decay and measurement of masses and widths
From a sample of 848 44 decays, we find
. Using a Dalitz plot analysis of this
three body decay, we find significant contributions from the channels
, , , , and
. We present also the values obtained for masses and widths of
the resonances and .Comment: 10 pages, 3 eps figure
Direct measurement of the pion valence quark momentum distribution, the pion light-cone wave function squared
We present the first direct measurements of the pion valence quark momentum
distribution which is related to the square of the pion light-cone wave
function. The measurements were carried out using data on diffractive
dissociation of 500 GeV/c into di-jets from a platinum target at
Fermilab experiment E791. The results show that the light-cone
asymptotic wave function, which was developed using perturbative QCD methods,
describes the data well for or more. We also
measured the transverse momentum distribution of the diffractive di-jets.Comment: 13 pages, 4 figure
Dalitz Plot Analysis of the Decay D^+ --> K^- pi^+ pi^+ and Indication of a Low-Mass Scalar K pi Resonance
We study the Dalitz plot of the decay D^+ --> K^- pi^+ pi^+ with a sample of
15090 events from Fermilab experiment E791. Modeling the decay amplitude as the
coherent sum of known K pi resonances and a uniform nonresonant term, we do not
obtain an acceptable fit. If we allow the mass and width of the K^*_0(1430) to
float, we obtain values consistent with those from PDG but the chi^2 per degree
of freedom of the fit is still unsatisfactory. A good fit is found when we
allow for the presence of an additional scalar resonance, with mass 797 +/- 19
+/- 43 MeV/c^2 and width 410 +/- 43 +/- 87 MeV/c^2. The mass and width of the
K^*_0(1430) become 1459 +/- 7 +/- 5 MeV/c^2 and 175 +/- 12 +/- 12 MeV/c^2,
respectively. Our results provide new information on the scalar sector in
hadron spectroscopy.Comment: Accepted for publication in Physical Review Letter
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