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E. M. Aitala,
S. Amato,
J. C. Anjos,
J. A. Appel,
D. Ashery,
S. Banerjee,
I. Bediaga,
G. Blaylock, S. B. Bracker,
P. R. Burchat, [......],
R. Weiss-Babai,
J. Wiener,
N. Witchey,
E. Wolin,
S. M. Yang,
D. Yi,
S. Yoshida,
R. Zaliznyak,
C. Zhang,
W. M. Dunwoodie
Physical review D: Particles and fields 08/2006; 74(5):59901.
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G A Alves,
S Amato,
J. C. Anjos,
J A Appel,
J. Astorga,
T. Bernard, S. B. Bracker,
L M Cremaldi,
W. D. Dagenhart,
C L Darling, [......],
W R Ross,
A F S Santoro,
M Sheaff,
M H G Souza,
C. Stoughton,
M. E. Streetman,
D J Summers,
S. F. Takach,
A. Wallace,
Z Wu
[show abstract]
[hide abstract]
ABSTRACT: Using data from Fermilab fixed-target experiment E769, we have measured particle-antiparticle production asymmetries for Lambda0 hyperons in 250 GeV/c pi+-, K+- and p -- nucleon interactions. The asymmetries are measured as functions of Feynman-x (x_F) and p_t^2 over the ranges -0.12<=x_F<=0.12 and 0<=p_t^2<=3 (GeV/c)^2 (for positive beam) and -0.12<=x_F<=0.4 and 0<=p_t^2<=10 (GeV/c)^2 (for negative beam). We find substantial asymmetries, even at x_F around zero. We also observe leading-particle-type asymmetries. These latter effects are qualitatively as expected from valence-quark content of the target and variety of projectiles studied.
04/2003;
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E M Aitala,
S Amato,
J C Anjos,
J A Appel,
D Ashery,
S Banerjee,
I Bediaga,
G Blaylock, S B Bracker,
P R Burchat, [......],
S Watanabe,
R Weiss-Babai,
J Wiener,
N Witchey,
E Wolin,
S M Yang,
D Yi,
S Yoshida,
R Zaliznyak,
C Zhang
[show abstract]
[hide abstract]
ABSTRACT: 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 Kpi 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.
Physical Review Letters 09/2002; 89(12):121801. · 7.37 Impact Factor
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E. M. Aitala,
S. Amato,
J. C. Anjos,
J. A. Appel,
D. Ashery,
S. Banerjee,
I. Bediaga,
G. Blaylock, S. B. Bracker,
P. R. Burchat, [......],
S. Watanabe,
R. Weiss-Babai,
J. Wiener,
N. Witchey,
E. Wolin,
S. M. Yang,
D. Yi,
S. Yoshida,
R. Zaliznyak,
C. Zhang
[show abstract]
[hide abstract]
ABSTRACT: Using data from the E791 fixed-target hadroproduction experiment at Fermilab, we have studied the Cabibbo-favored but phase-space-suppressed decay D0→K-K-K+π+. We find the decay rate for this mode to be (0.54±0.16±0.08)×10-2 times that for the normalization mode D0→K-π-π+π+. We observe a clear signal for D0→φK-π+ which is consistent with producing 0.7±0.3 of the D0→K-K-K+π+ signal. In the context of simple models, we use our measurements to estimate the importance of decay amplitudes that produce extra quark-antiquark pairs from the vacuum relative to those that do not.
Phys. Rev. D. 11/2001; 64(11).
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E M Aitala,
S Amato,
J C Anjos,
J A Appel,
D Ashery,
S Banerjee,
I Bediaga,
G Blaylock, S B Bracker,
P R Burchat, [......],
S Watanabe,
R Weiss-Babai,
J Wiener,
N Witchey,
E Wolin,
S M Yang,
D Yi,
S Yoshida,
R Zaliznyak,
C Zhang
[show abstract]
[hide abstract]
ABSTRACT: We report results of a search for flavor-changing neutral current (FCNC), lepton flavor, and lepton-number violating decays of the D0 (and its antiparticle) into three and four bodies. Using data from Fermilab charm hadroproduction experiment E791, we examine modes with two leptons (muons or electrons) and a rho(0), K( *0), or straight phi vector meson or a nonresonant pi(pi), Kpi, or KK pair of pseudoscalar mesons. No evidence for any of these decays is found. Therefore, we present branching-fraction upper limits at 90% confidence level for the 27 decay modes examined (18 new).
Physical Review Letters 05/2001; 86(18):3969-72. · 7.37 Impact Factor
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E M Aitala,
S Amato,
J C Anjos,
J A Appel,
D Ashery,
S Banerjee,
I Bediaga,
G Blaylock, S B Bracker,
P R Burchat, [......],
S Watanabe,
R Weiss-Babai,
J Wiener,
N Witchey,
E Wolin,
S M Yang,
D Yi,
S Yoshida,
R Zaliznyak,
C Zhang
[show abstract]
[hide abstract]
ABSTRACT: We have studied the diffractive dissociation into dijets of 500 GeV/c pions scattering coherently from carbon and platinum targets. Extrapolating to asymptotically high energies (where t(min)-->0), we find that when the per-nucleus cross section for this process is parametrized as sigma = sigma0Aalpha, alpha has values near 1.6, the exact result depending on jet transverse momentum. These values are in agreement with those predicted by theoretical calculations of color-transparency.
Physical Review Letters 05/2001; 86(21):4773-7. · 7.37 Impact Factor
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E M Aitala,
S Amato,
J C Anjos,
J A Appel,
D Ashery,
S Banerjee,
I Bediaga,
G Blaylock, S B Bracker,
P R Burchat, [......],
S Watanabe,
R Weiss-Babai,
J Wiener,
N Witchey,
E Wolin,
S M Yang,
D Yi,
S Yoshida,
R Zaliznyak,
C Zhang
[show abstract]
[hide abstract]
ABSTRACT: 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 pi(-) into dijets from a platinum target at Fermilab experiment E791. The results show that the /q&q> light-cone asymptotic wave function describes the data well for Q2 approximately 10 (GeV/c)(2) or more. We also measured the transverse momentum distribution of the diffractive dijets.
Physical Review Letters 05/2001; 86(21):4768-72. · 7.37 Impact Factor
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E M Aitala,
S Amato,
J C Anjos,
J A Appel,
D Ashery,
S Banerjee,
I Bediaga,
G Blaylock, S B Bracker,
P R Burchat, [......],
S Watanabe,
R Weiss-Babai,
J Wiener,
N Witchey,
E Wolin,
S M Yang,
D Yi,
S Yoshida,
R Zaliznyak,
C Zhang
[show abstract]
[hide abstract]
ABSTRACT: From a sample of 1172 +/- 61 D(+)-->pi(-)pi(+)pi(+) decays, we find gamma(D(+)-->pi(-)pi(+)pi(+))/gamma(D(+)-->K-pi(+)pi(+)) = 0.0311 +/- 0.0018(+0.0016)(-0.0026). Using a coherent amplitude analysis to fit the Dalitz plot of these decays, we find strong evidence that a scalar resonance of mass 478(+24)(-23) +/- 17 MeV/c(2) and width 324(+42)(-40) +/- 21 MeV/c(2) accounts for approximately half of all decays.
Physical Review Letters 02/2001; 86(5):770-4. · 7.37 Impact Factor
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E M Aitala,
S Amato,
J C Anjos,
J A Appel,
D Ashery,
S Banerjee,
I Bediaga,
G Blaylock, S B Bracker,
P R Burchat, [......],
S Watanabe,
R Weiss-Babai,
J Wiener,
N Witchey,
E Wolin,
S M Yang,
D Yi,
S Yoshida,
R Zaliznyak,
C Zhang
[show abstract]
[hide abstract]
ABSTRACT: From a sample of 848+/-44 D(+)(s)-->pi(-)pi(+)pi(+) decays, we find gamma(D(+)(s)-->pi(-)pi(+)pi(+))/gamma(D(+)(s)-->straight phipi(+)) = 0.245+/-0.028(+0.019)(-0.012). Using a Dalitz plot analysis of this three body decay, we find significant contributions from the channels rho(0)(770)pi(+), rho(0)(1450)pi(+), f(0)(980)pi(+), f(2)(1270)pi(+), and f(0)(1370)pi(+). We also present the values obtained for masses and widths of the resonances f(0)(980) and f(0)(1370).
Physical Review Letters 02/2001; 86(5):765-9. · 7.37 Impact Factor
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E. M. Aitala,
S. Amato,
J. C. Anjos,
J. A. Appel,
D. Ashery,
S. Banerjee,
I. Bediaga,
G. Blaylock, S. B. Bracker,
P. R. Burchat, [......],
S. Watanabe,
R. Weiss-Babai,
J. Wiener,
N. Witchey,
E. Wolin,
S.M. Yang,
D. Yi,
S. Yoshida,
R. Zaliznyak,
C. Zhang
[show abstract]
[hide abstract]
ABSTRACT: We present a study of correlations between D and
[`(D)]{\overline D}
mesons produced in 500 GeV/cπ−-nucleon interactions, based on data from experiment E791 at Fermilab. We have fully reconstructed 791 44 charm meson pairs to study correlations between the transverse and longitudinal momenta of the two D mesons and the relative production rates for different types of D meson pairs. We see slight correlations between the longitudinal momenta of the D and the
[`(D)]{\bar D}
, and significant correlations between the azimuthal angle of the D and the
[`(D)]{\bar D}
. The experimental distributions are compared to a next-to-leading-order QCD calculation and to predictions of the PYTHIA/JETSET Monte Carlo event generator. We observe less correlation between transverse momenta and different correlations between longitudinal momenta than these models predict for the default values of the model parameters. Better agreement between data and theory might be achieved by tuning the model parameters or by adding higher order perturbative terms, thus contributing to a better understanding of charm production.The relative production rates for the four sets of charm pairs,
D0[`(D)]0, D0 D-, D+[`(D)]0, D+ D-D^0{{\overline D}^0}, D^0 D^{-}, D^+{{\overline D}^0}, D^+ D^{-}
as calculated in the PYTHIA/JETSET event generator with the default parameters, agree with data as far as the relative ordering, but predict too many
D+ [`(D)]0D^+ {{\overline D}^0}
pairs and too few
D+ D-D^+ D^{-}
pairs.
EPJ direct 11/2000; 1(1):1-67.
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E. M. Aitala,
S Amato,
J. C. Anjos,
D. Ashery,
S Banerjee,
I. Bediaga,
G Blaylock, S. B. Bracker,
P R Burchat,
R. A. Burnstein,
H. S. Carvalho
[show abstract]
[hide abstract]
ABSTRACT: We report the results of a search for the flavor-changing neutral-current decays D in data from Fermilab charm hadroproduction experiment E791. No signal above background is found, and we obtain upper limits on branching fractions, B(D , at the 90% confidence level.
10/1999;
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S Amato,
J. C. Anjos,
D. Ashery,
S Banerjee,
I. Bediaga,
G Blaylock, S. B. Bracker,
P R Burchat,
R. A. Burnstein,
T Carter,
H. S. Carvalho
[show abstract]
[hide abstract]
ABSTRACT: We report results of the first search for the pentaquark P cs which is predicted to be a doublet of states: P cs = jcsuudi and P cs = jcsddui. A search was made for the decay P cs ! OEp in data from Fermilab experiment E791, in which 500 GeV/c beam interacted with nuclear targets. We present upper limits at 90% confidence level for the ratio of cross section times branching fraction of this decay to that for the decay D . The upper limits are 0.031 and 0.063 for M(P cs ) = 2.75 and 2.86 GeV/c , respectively, assuming a P cs lifetime of 0.4 ps.
10/1999;
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[show abstract]
[hide abstract]
ABSTRACT: We present results of a search for D mixing and doubly-Cabibbosuppressed in Fermilab experiment E791, a fixed-target charm hadroproduction experiment. We look for evidence of mixing in the decay chain D ! D ! (K or K). If the charge of the pion from the D decay is the same as the charge of the kaon from the D decay (a "wrong-sign" event), mixing may have occurred. Mixing can be distinguished from other sources of wrong-sign events (such as doubly-Cabibbosuppressed decays) by analyzing the distribution of decay times. We see no evidence of mixing. Allowing for CP violation in the interference between DCS and mixing amplitudes our fitted ratio for mixed to unmixed decay rates is r mix = (0:39 Gamma0:32 Sigma 0:16)%. This corresponds to a 90% CL upper limit of r mix ! 0:85%. The sensitivity of this result is comparable to that of previous measurements, but the assumptions made in fitting the data are notably more general. We present results from many fits to our data under various assump2 tions. If we assume r mix = 0, we find a two-sigma wrong-sign enhancement in the K mode which we ascribe to doubly Cabibbo-suppressed decays. The ratios of doubly Cabibbo-suppressed decays to Cabibbo-favored decays are 12.15.Ff, 13.25.Ft, 14.40.Lb Typeset using REVT E I.
10/1999;
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E. M. Aitala,
S Amato,
J. C. Anjos,
D. Ashery,
S Banerjee,
I. Bediaga,
G Blaylock, S. B. Bracker,
P R Burchat,
R. A. Burnstein,
T Carter,
H. S. Carvalho
[show abstract]
[hide abstract]
ABSTRACT: this paper. We use data from experiment E791[14] which recorded 2 Theta 10 500 GeV/c -nucleon interactions during the 1991/92 fixed-target run at Fermilab. The segmented target consisted of one platinum foil and four diamond foils separated by gaps of 1.34 to 1.39 cm. Each foil was approximately 0.4% of an interaction length thick (0.5 mm for platinum and 1.6 mm for diamond). Pentaquarks with lifetimes in the range expected and produced with momenta in the range for which the detector has good geometric acceptance should decay most frequently in the air gaps between the foils. As for other charm signals, the backgrounds for pentaquark signals should be lower in these gaps. For comparison, the average decay length of a D s of momentum 80 GeV/c, roughly the mean value we observe, is approximately 6 mm. There were six planes of silicon microstrip detectors (SMDs) and eight proportional wire chambers (PWCs) used to track the beam particles. The downstream detector consisted of 17 planes of SMDs for vertex detection, 35 drift chamber planes, two PWCs, and two magnets for momentum analysis. Two multicell threshold counters[15] with nominal pion thresholds of 6 GeV/c and 11 GeV/c provided charged , K, and p identification. Electromagnetic and hadronic calorimeters were used for online triggering and for electron identification. Two planes of scintillators behind an equivalent of 2.4 m of iron provided muon identification. An interaction pre-trigger required a beam particle and an interaction in the 4 target. A very loose transverse energy trigger based on the energy deposited in the calorimeters and a fast data acquisition system [16] allowed us to collect data at a rate of up to 30 Mbytes/s with 50s/event dead time and to write data to tape at a rate of 10 Mbytes/s. ...
10/1999;
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Fermilab E Collaboration,
E. M. Aitala,
S Amato,
J. C. Anjos,
D. Ashery,
S Banerjee,
I. Bediaga,
G Blaylock, S. B. Bracker,
P R Burchat, [......],
P Gagnon,
C. Gobel,
K Gounder,
A M Halling,
G. Herrera,
G Hurvits,
C James,
P A Kasper,
S Kwan,
D C Langs
[show abstract]
[hide abstract]
ABSTRACT: We measure the neutral D total forward cross section and the differential cross sections as functions of Feynman-x (x F ) and transverse momentum squared for 500 GeV/c --nucleon interactions. The results are obtained from 88 990Sigma460 reconstructed neutral D mesons from Fermilab experiment E791 using the decay channels D (and charge conjugates). We extract fit parameters from the differential cross sections and provide the first direct measurement of the turnover point in the x F distribution, 0.0131Sigma0.0038. We measure an absolute D (x F ?0) cross section of 15:4 Gamma barns/nucleon (assuming a linear A dependence). The differential and total forward cross sections are compared to theoretical predictions and to results of previous experiments.
10/1999;
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E. M. Aitala,
S Amato,
J. C. Anjos,
D. Ashery,
S Banerjee,
I. Bediaga,
G Blaylock, S. B. Bracker,
P R Burchat,
R. A. Burnstein,
T Carter,
H. S. Carvalho
10/1999;
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[show abstract]
[hide abstract]
ABSTRACT: We present measurements of the production of D s mesons relative to D s mesons as functions of x F and of p t for a sample of 2445 D s decays to OE. The D s mesons were produced in Fermilab experiment E791 with 500 GeV/c mesons incident on one platinum and four carbon foil targets. The acceptance-corrected integrated asymmetry in the x F range Gamma0:1 to 0.5 for D s mesons is 0.032 Sigma 0.022 Sigma 0.022, consistent with no net asymmetry. We compare the results as functions of x F and to predictions and to the large production asymmetry observed for mesons in the same experiment. These comparisons support the hypothesis that production asymmetries come from the fragmentation process and not from the charm quark production itself.
10/1999;
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E. M. Aitala,
S Amato,
J. C. Anjos,
D. Ashery,
S Banerjee,
I. Bediaga,
G Blaylock, S. B. Bracker,
P R Burchat,
R. A. Burnstein,
T Carter,
N K Copty
[show abstract]
[hide abstract]
ABSTRACT: From a sample of 2722 Sigma 78 c decaying to the pK final state, we have observed, in the hadroproduction experiment E791 at Fermilab, 143 Sigma 20 Sigma c and 122 Sigma 18 Sigma c through their decays to . The mass difference M (Sigma c ) is measured to be (167:38 Sigma 0:29 Sigma 0:15) MeV; for M (Sigma c ), we find (167:76 Sigma 0:29 Sigma 0:15) MeV. The rate c production from decays of the Sigma c triplet is (22 Sigma 2 Sigma 3) % of the total c production assuming equal rate of production from all three, as measured for Sigma c . We do not observe a statistically significant Sigma c baryon-antibaryon production asymmetry. The x F and p t spectra c from Sigma c decays are observed to be similar to those for all c 's produced.
10/1999;
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[show abstract]
[hide abstract]
ABSTRACT: We report the results of a precise measurement of the D s meson lifetime based on 1662 Sigma 56 fully reconstructed D s ! OE decays, from the charm hadroproduction experiment E791 at Fermilab. Using an unbinned maximum likelihood fit, we measure the D s lifetime to be 0:518 Sigma 0:014 Sigma 0:007 ps. The ratio of the measured D s lifetime to the world average D lifetime [1] is 1:25 Sigma 0:04. This result differs from unity by six standard deviations, indicating significantly different lifetimes for the D s and the D PACS: 13.25.Ft, 14.40.Lb Precise measurements of the lifetimes of the weakly decaying charm mesons are useful for understanding the contributions of various weak decay mechanisms. Despite the fact that they are all tied to the charm quark decay, the decays of the ground-state charm mesons can have different contributions from the four first-order processes (two spectator, W-annihilation, and W-exchange), and the lifetimes are, in fact, quite different [1]: ) : (D ) : (D s ) = 2:5 : 1 : 1:1 The least well measured among these lifetimes is that of the D s , which is known only to about the 4% level [2]. It is clear that there is a very large difference between the lifetime of the D and that of the D or D s . However, the current measurements are only suggestive of a difference between the lifetimes of the and the D s : = 1:13 Sigma 0:04 ( 3oe difference from unity ): A more precise measurement of the lifetime of the D s could more clearly establish whether the lifetimes of the D and D s are indeed different.
10/1999;
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S Amato,
J. C. Anjos,
D. Ashery,
S Banerjee,
I. Bediaga,
G Blaylock, S. B. Bracker,
P R Burchat,
R. A. Burnstein,
T Carter,
H. S. Carvalho
[show abstract]
[hide abstract]
ABSTRACT: We report a measurement of the branching ratio B(D ` )/ ` ) from the Fermilab charm hadroproduction experiment E791. Based on signals of 49 Sigma 17 events in the D e mode and 54 Sigma 18 events in the D mode, we measure e )=B(D e ) = 0:045 Sigma 0:014 Sigma 0:009, and )=B(D ) = 0:051 Sigma 0:015 Sigma 0:009: Combining the results from both the electronic and muonic modes, we obtain ` ) = 0:047 Sigma 0:013: This result is compared to theoretical predictions.
10/1999;
