85 research outputs found
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
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
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
Free Radical Exposure Creates Paler Carotenoid-Based Ornaments: A Possible Interaction in the Expression of Black and Red Traits
Oxidative stress could be a key selective force shaping the expression of colored traits produced by the primary animal pigments in integuments: carotenoids and melanins. However, the impact of oxidative stress on melanic ornaments has only recently been explored, whereas its role in the expression of carotenoid-based traits is not fully understood. An interesting study case is that of those animal species simultaneously expressing both kinds of ornaments, such as the red-legged partridge (Alectoris rufa). In this bird, individuals exposed to an exogenous source of free radicals (diquat) during their development produced larger eumelanin-based (black) plumage traits than controls. Here, we show that the same red-legged partridges exposed to diquat simultaneously developed paler carotenoid-based ornaments (red beak and eye rings), and carried lower circulating carotenoid levels as well as lower levels of some lipids involved in carotenoid transport in the bloodstream (i.e., cholesterol). Moreover, partridges treated with a hormone that stimulates eumelanin production (i.e., alpha-melanocyte-stimulating hormone) also increased blood carotenoid levels, but this effect was not mirrored in the expression of carotenoid-based traits. The redness of carotenoid-based ornaments and the size of a conspicuous eumelanic trait (the black bib) were negatively correlated in control birds, suggesting a physiological trade-off during development. These findings contradict recent studies questioning the sensitivity of carotenoids to oxidative stress. Nonetheless, the impact of free radicals on plasma carotenoids seems to be partially mediated by changes in cholesterol metabolism, and not by direct carotenoid destruction/consumption. The results highlight the capacity of oxidative stress to create multiple phenotypes during development through differential effects on carotenoids and melanins, raising questions about evolutionary constraints involved in the production of multiple ornaments by the same organism
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
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. Lett., 3, pp. 181-183Goldhaber, G., Goldhaber, S., Lee, W., Pais, A., Influence of Bose-Einstein statistics on the antiproton-proton annihilation process (1960) Phys. Rev., 120, pp. 300-312Kopylov, G.I., Podgoretsky, M.I., Correlations of identical particles emitted by highly excited nuclei (1972) Sov. J. Nucl. Phys., 15, pp. 219-223Kopylov, G.I., Podgoretsky, M.I., Multiple production and interference of particles emitted by moving sources (1974) Sov. J. Nucl. Phys., 18, pp. 336-341Kopylov, G.I., Like particle correlations as a tool to study the multiple production mechanism (1974) Phys. Lett. B, 50, pp. 472-474Abbiendi, G., Transverse and longitudinal Bose-Einstein correlations in hadronic Z0 decays (2000) Eur. Phys. J. C, 16, pp. 423-433. , arxiv:hep-ex/0002062Chekanov, S., Bose-Einstein correlations in one and two dimensions in deep inelastic scattering (2004) Phys. Lett. B, 583, pp. 231-246. , arxiv:hep-ex/0311030Aamodt, K., Two-pion Bose-Einstein correlations in pp collisions at s=900GeV (2010) Phys. Rev. D, 82. , arxiv:1007.0516Beker, H., MT dependence of boson interferometry in heavy ion collisions at the CERN SPS (1995) Phys. Rev. Lett., 74, pp. 3340-3343Adamczyk, L., Beam-energy-dependent two-pion interferometry and the freeze-out eccentricity of pions measured in heavy ion collisions at the STAR detector (2015) Phys. Rev. C, 92. , arxiv:1403.4972Adams, J., Experimental and theoretical challenges in the search for the quark-gluon plasma: the STAR Collaboration's critical assessment of the evidence from RHIC collisions (2005) Nucl. Phys. A, 757, pp. 102-183. , arxiv:nucl-ex/0501009Adcox, K., Formation of dense partonic matter in relativistic nucleus-nucleus collisions at RHIC: experimental evaluation by the PHENIX Collaboration (2005) Nucl. Phys. A, 757, pp. 184-283. , arxiv:nucl-ex/0410003Back, B.B., The PHOBOS perspective on discoveries at RHIC (2005) Nucl. Phys. A, 757, pp. 28-101. , arxiv:nucl-ex/0410022Arsene, I., Quark-gluon plasma and color glass condensate at RHIC? The perspective from the BRAHMS experiment (2005) Nucl. Phys. A, 757, pp. 1-27. , arxiv:nucl-ex/0410020Akkelin, S.V., Sinyukov, Y.M., The HBT-interferometry of expanding sources (1995) Phys. Lett. B, 356, pp. 525-530Alexander, G., Cohen, I., Levin, E., The dependence of the emission size on the hadron mass (1999) Phys. Lett. B, 452, pp. 159-166. , arxiv:hep-ph/9901341Kittel, W., Bose-Einstein correlations in Z fragmentation and other reactions (2001) Acta Phys. Pol. B, 32, pp. 3927-3972. , arxiv:hep-ph/0110088Chajȩcki, Z., Femtoscopy in hadron and lepton collisions: RHIC results and world systematics (2009) Acta Phys. Pol. B, 40, pp. 1119-1136. , arxiv:0901.4078Aggarwal, M.M., Pion femtoscopy in p+p collisions at s=200GeV (2011) Phys. Rev. C, 83. , arxiv:1004.0925Engelfried, J., The SELEX phototube RICH detector (1999) Nucl. Instrum. Methods A, 431, pp. 53-69. , arxiv:hep-ex/9811001Engelfried, J., The E781 (SELEX) RICH detector (1998) Nucl. Instrum. Methods A, 409, pp. 439-442Sjöstrand, T., Mrenna, S., Skands, P., PYTHIA 6.4 physics and manual (2006) J. High Energy Phys., 5. , arxiv:hep-ph/0603175v2Chajȩcki, Z., Lisa, M., Global conservation laws and femtoscopy of small systems (2008) Phys. Rev. C, 78. , arxiv:0803.0022Lednický, R., Lyuboshitz, V.L., Erazmus, B., Nouais, D., How to measure which sort of particles was emitted earlier and which later (1996) Phys. Lett. B, 373, pp. 30-34Voloshin, S., Lednický, R., Panitkin, S., Xu, N., Relative space-time asymmetries in pion and nucleon production in noncentral nucleus-nucleus collisions at high-energies (1997) Phys. Rev. Lett., 79, pp. 4766-4769. , arxiv:nucl-th/9708044Pratt, S., Shapes and sizes from non-identical-particle correlations (2007) Braz. J. Phys., 37, pp. 871-876. , arxiv:nucl-th/0612006Lednický, R., Finite-size effect on two-particle production (2008) J. Phys. G, Nucl. Part. Phys., 35Lednický, R., Lyuboshitz, V.V., Lyuboshitz, V.L., Final-state interactions in multichannel quantum systems and pair correlations of nonidentical and identical particles at low relative velocities (1998) Phys. At. Nucl., 61, pp. 2050-2063Bowler, M.G., Coulomb corrections to Bose-Einstein corrections have greatly exaggerated (1991) Phys. Lett. B, 270, pp. 69-74Sinyukov, Y., Lednický, R., Akkelin, S.V., Pluta, J., Erazmus, B., Coulomb corrections to Bose-Einstein corrections have greatly exaggerated (1998) Phys. Lett. B, 432, pp. 248-257Adams, J., Pion interferometry in Au+Au collisions at sNN=200GeV (2005) Phys. Rev. C, 71. , arxiv:nucl-ex/0411036Skands, P.Z., Tuning Monte Carlo generators: the Perugia tunes (2010) Phys. Rev. D, 82. , arxiv:1005.3457Abelev, B., Charged kaon femtoscopic correlations in pp collisions at s=7TeV (2013) Phys. Rev. D, 87. , arxiv:1212.5958v2Khachatryan, V., Measurement of Bose-Einstein correlations in pp collisions at s = 0.9 and 7 TeV (2011) J. High Energy Phys., 5. , arxiv:1101.3518Akkelin, S.V., Sinyukov, Y.M., Deciphering nonfemtoscopic two-pion correlations in p+p collisions with simple analytical models (2012) Phys. Rev. D, 85. , arxiv:1106.5120Lednický, R., Progulova, T.B., Influence of resonances on Bose-Einstein correlations of identical pions (1992) Z. Phys. C, 55, pp. 295-305Lisa, M., Pratt, S., Soltz, R., Wiedemann, U., Femtoscopy in relativistic heavy ion collisions: two decades of progress (2005) Annu. Rev. Nucl. Part. Sci., 55, pp. 357-402. , arxiv:nucl-ex/0505014Pratt, S., Pion interferometry for exploding sources (1984) Phys. Rev. Lett., 53, pp. 1219-1221Abbiendi, G., Bose-Einstein study of position-momentum correlations of charged pions in hadronic Z0 decays (2007) Eur. Phys. J. C, 52, pp. 787-803. , arxiv:0708.1122Achard, P., Test of the τ-model of Bose-Einstein correlations and reconstruction of the source function in hadronic Z-boson decay at LEP (2011) Eur. Phys. J. C, 71, p. 1648. , arxiv:1105.4788Aamodt, K., Femtoscopy of pp collisions at s = 0.9 and 7 TeV at the LHC with two-pion Bose-Einstein correlations (2011) Phys. Rev. D, 84. , arxiv:1101.3665Wiedemann, U.A., Heinz, U.W., Resonance contributions to Hanbury-Brown-Twiss correlation radii (1997) Phys. Rev. C, 56, pp. 3265-3286. , arxiv:nucl-th/9611031Werner, K., Karpenko, I., Pierog, T., Bleicher, M., Mikhailov, K., Evidence for hydrodynamic evolution in proton-proton scattering at 900 GeV (2011) Phys. Rev. C, 83. , arxiv:1010.0400Humanic, T.J., Predictions for two-pion correlations for s=14TeV proton-proton collisions (2007) Phys. Rev. C, 76. , arxiv:nucl-th/0612098Alexopoulos, T., Study of source size in pp- collisions at s=1.8TeV using pion interferometry (1993) Phys. Rev. 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
- …