58 research outputs found
First Observation of the Doubly Charmed Baryon Xi_cc^+
We observe a signal for the doubly charmed baryon Xi_cc^+ in the charged
decay mode Xi_cc^+ --> Lambda_c^+ K- pi+ in data from SELEX, the charm
hadro-production experiment at Fermilab. We observe an excess of 15.9 events
over an expected background of 6.1 +/- 0.5 events, a statistical significance
of 6.3sigma. The observed mass of this state is (3519 +/- 1) MeV/c^2. The
Gaussian mass width of this state is 3MeV/c^2, consistent with resolution; its
lifetime is less than 33fsec at 90% confidence.Comment: 5 pages, 3 figures, accepted for publication in Physical Review
Letter
First Measurement of pi e -> pi e gamma Pion Virtual Compton Scattering
Pion Virtual Compton Scattering (VCS) via the reaction pi e --> pi e gamma
was observed in the Fermilab E781 SELEX experiment. SELEX used a 600 GeV/c pi-
beam incident on target atomic electrons, detecting the incident pi- and the
final state pi-, electron and gamma. Theoretical predictions based on chiral
perturbation theory are incorporated into a Monte Carlo simulation of the
experiment and are compared to the data. The number of reconstructed events (9)
and their distribution with respect to the kinematic variables (for the
kinematic region studied) are in reasonable accord with the predictions. The
corresponding pi- VCS experimental cross section is sigma=38.8+-13 nb, in
agreement with the theoretical expectation sigma=34.7 nb.Comment: 10 pages, 12 figures, 4 tables, 25 references, SELEX home page is
http://fn781a.fnal.gov/, revised July 21, 2002 in response to journal referee
Comment
Observation of the Cabibbo-suppressed decay Xi_c+ -> p K- pi+
We report the first observation of the Cabibbo-suppressed charm baryon decay
Xi_c+ -> p K- pi+. We observe 150 +- 22 events for the signal. The data were
accumulated using the SELEX spectrometer during the 1996-1997 fixed target run
at Fermilab, chiefly from a 600 GeV/c Sigma- beam. The branching fractions of
the decay relative to the Cabibbo-favored Xi_c+ -> Sigma+ K- pi+ and Xi_c+ ->
X- pi+ pi+ are measured to be B(Xi_c+ -> p K- pi+)/B(Xi_c+ -> Sigma+ K- pi+) =
0.22 +- 0.06 +- 0.03 and B(Xi_c+ -> p K- pi+)/B(Xi_c+ -> X- pi+ pi+) = 0.20 +-
0.04 +- 0.02, respectively.Comment: 5 pages, RevTeX, 3 figures (postscript), Submitted to Phys. Rev. Let
First observation of a narrow charm-strange meson DsJ(2632) -> Ds eta and D0 K+
We report the first observation of a charm-strange meson DsJ(2632) at a mass
of 2632.6+/-1.6 MeV/c^2 in data from SELEX, the charm hadro-production
experiment E781 at Fermilab. This state is seen in two decay modes, Ds eta and
D0 K+. In the Ds eta decay mode we observe an excess of 49.3 events with a
significance of 7.2sigma at a mass of 2635.9+/-2.9 MeV/c^2. There is a
corresponding peak of 14 events with a significance of 5.3sigma at 2631.5+/-1.9
MeV/c^2 in the decay mode D0 K+. The decay width of this state is <17 MeV/c^2
at 90% confidence level. The relative branching ratio Gamma(D0K+)/Gamma(Dseta)
is 0.16+/-0.06. The mechanism which keeps this state narrow is unclear. Its
decay pattern is also unusual, being dominated by the Ds eta decay mode.Comment: 5 pages, 3 included eps figures. v2 as accepted for publication by
PR
Measurement of the Ds lifetime
We report precise measurement of the Ds meson lifetime. The data were taken
by the SELEX experiment (E781) spectrometer using 600 GeV/c Sigma-, pi- and p
beams. The measurement has been done using 918 reconstructed Ds. The lifetime
of the Ds is measured to be 472.5 +- 17.2 +- 6.6 fs, using K*(892)0K+- and phi
pi+- decay modes. The lifetime ratio of Ds to D0 is 1.145+-0.049.Comment: 5 pages, 2 figures submitted to Phys. Lett.
Confirmation of the Double Charm Baryon Xi_cc+ via its Decay to p D+ K-
We observes a signal for the double charm baryon Xi_cc+ in the charged decay
mode Xi_cc+ -> p D+ K- to complement the previously reported decay Xi_cc+ ->
Lambda_c K- pi+ in data from SELEX, the charm hadro-production experiment
(E781) at Fermilab. In this new decay mode we observe an excess of 5.62 events
over an expected background estimated by event mixing to be 1.38+/-0.13 events.
The Poisson probability that a background fluctuation can produce the apparent
signal is less than 6.4E-4. The observed mass of this state is
(3518+/-3)MeV/c^2, consistent with the published result. Averaging the two
results gives a mass of (3518.7+/-1.7)MeV/c^2. The observation of this new weak
decay mode confirms the previous SELEX suggestion that this state is a double
charm baryon. The relative branching ratio Gamma(Xi_cc+ -> pD+K-)/Gamma(Xi_cc+
-> Lambda_c K- pi+) = 0.36+/-0.21.Comment: 11 pages, 6 included eps figures. v2 includes improved statistical
method to determine significance of observation. Submitted to PL
The transverse momentum dependence of charged kaon Bose-Einstein correlations in the SELEX experiment
CNPQ - CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICOFAPESP - FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULOWe report the measurement of the one-dimensional charged kaon correlation functions using 600GeV/c σ-, π- and 540GeV/c p beams from the SELEX (E781) experiment at the Fermilab Tevatron. K±K± correlation functions are studied for three transverse pair momentum, kT, ranges and parameterized by a Gaussian form. The emission source radii, R, and the correlation strength, λ, are extracted. The analysis shows a decrease of the source radii with increasing kaon transverse pair momentum for all beam types. © 2015 The Authors.We report the measurement of the one-dimensional charged kaon correlation functions using 600GeV/c σ-, π- and 540GeV/c p beams from the SELEX (E781) experiment at the Fermilab Tevatron. K±K± correlation functions are studied for three transverse pair momentum, kT, ranges and parameterized by a Gaussian form. The emission source radii, R, and the correlation strength, λ, are extracted. The analysis shows a decrease of the source radii with increasing kaon transverse pair momentum for all beam types.753458464CNPQ - CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICOFAPESP - FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULOCNPQ - CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICOFAPESP - FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULOSem informaçãoSem informaçãoRuss, J.S., Akchurin, N., Andreev, V.A., First charm hadroproduction results from SELEX (1998) ICHEP'98 Proc. Int. Conf. on High Energy Physics II, p. 1259. , arxiv:hep-ex/9812031Goldhaber, G., Fowler, W.B., Goldhaber, S., Hoang, T.F., Kalogeropoulos, T.E., Powell, W.M., Pion-pion correlations in antiproton annihilation events (1959) Phys. Rev. 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D, 48, pp. 1931-1942Csorgo, T., Kittel, W., Metzger, W.J., Novák, T., Parametrization of Bose-Einstein correlations and reconstruction of the space-time evolution of pion production in e+e- annihilation (2008) Phys. Lett. B, 663, pp. 214-216. , arxiv:0803.3528Bialas, A., Kucharczyk, M., Palka, H., Zalewski, K., Mass dependence of HBT correlations in e+e- annihilation (2000) Phys. Rev. D, 62. , arxiv:hep-ph/0006290Alexander, G., Open questions related to Bose-Einstein correlations in e+e- → hadrons (2004) Acta Phys. Pol. B, 35, pp. 69-76. , arxiv:hep-ph/0311114Alexander, G., Mass and transverse mass effects on the hadron emitter size (2001) Phys. Lett. B, 506, pp. 45-51. , arxiv:hep-ph/0101319The authors are indebted to the staff of Fermi National Accelerator Laboratory and for invaluable technical support from the staffs of collaborating institutions. This project was supported in part by Bundesministerium für Bildung, Wissenschaft, Forschung und Technologie, Consejo Nacional de Ciencia y Tecnología (CONACyT), Conselho Nacional de Desenvolvimento Científico e Tecnológico, Fondo de Apoyo a la Investigación (UASLP), Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP), the Israel Science Foundation founded by the Israel Academy of Sciences and Humanities, Istituto Nazionale di Fisica Nucleare (INFN), the International Science Foundation (ISF), the National Science Foundation, NATO, the Russian Academy of Sciences, the Russian Ministry of Science and Technology, the Russian Foundation for Basic Research (research project No. 11-02-01302-a), the Secretaría de Educación Pública (Mexico), the Turkish Scientific and Technological Research Board (TÜBİTAK), and the U.S. Department of Energy. We thank ITEP and National Research Nuclear University MEPhI (Moscow Engineering Physics Institute) for providing computing powers and support for data analysis and simulations. The authors also would like to thank Prof. Michael Lisa and Prof. Richard Lednický for helpful comments and fruitful discussions
Precision measurements of the Lambda_c+ and D0 lifetimes
We report new precision measurements of the lifetimes of the Lambda_c+ and D0
from SELEX, the charm hadro-production experiment at Fermilab. Based upon 1630
Lambda_c+ and 10210 D0 decays we observe lifetimes of tau[Lambda_c+] = 198.1 +-
7.0 +- 5.6 fs and tau[D0] = 407.9 +- 6.0 +- 4.3 fsComment: 5 pages, RevTeX, 3 figures (postscript), Submitted to Phys. Rev. Let
Polarization of Σ
We show that Sigma(+) hyperons produced by 800 GeV/c protons on targets of Be and Cu have significant polarizations (15-20%). These polarizations persist at values of p(t)approximate to2 GeV/c and a wide range of x(F). The polarizations from the Cu target are consistently less than from Be. The average ratio of the Sigma(+) polarization from Cu to that from Be is 0.68+/-0.08
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