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12 results on '"Comfort JR"'

1. Test of charge conjugation invariance.

Author

Nefkens BM, Prakhov S, Gårdestig A, Allgower CE, Bekrenev V, Briscoe WJ, Clajus M, Comfort JR, Craig K, Grosnick D, Isenhower D, Knecht N, Koetke D, Koulbardis A, Kozlenko N, Kruglov S, Lolos G, Lopatin I, Manley DM, Manweiler R, Marusić A, McDonald S, Olmsted J, Papandreou Z, Peaslee D, Phaisangittisakul N, Price JW, Ramirez AF, Sadler M, Shafi A, Spinka H, Stanislaus TD, Starostin A, Staudenmaier HM, Supek I, and Tippens WB

Abstract

We report on the first determination of upper limits on the branching ratio (BR) of eta decay to pi0pi0gamma and to pi0pi0pi0gamma. Both decay modes are strictly forbidden by charge conjugation (C) invariance. Using the Crystal Ball multiphoton detector, we obtained BR(eta-->pi0pi0gamma)<5 x 10(-4) at the 90% confidence level, in support of C invariance of isoscalar electromagnetic interactions of the light quarks. We have also measured BR(eta-->pi0pi0pi0gamma)<6 x 10(-5) at the 90% confidence level, in support of C invariance of isovector electromagnetic interactions.

Published
2005
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2. Dynamics of the pi(-)p-->pi(0)pi(0)n reaction for p(pi(-))<750 MeV/c.

Author

Craig K, Comfort JR, Allgower CE, Bekrenev V, Berger E, Briscoe WJ, Clajus M, Draper B, Grosnick D, Isenhower D, Knecht N, Koetke D, Koulbardis A, Kozlenko N, Kruglov S, Lolos GJ, Lopatin I, Manley DM, Manweiler R, Marusić A, McDonald S, Nefkens BM, Olmsted J, Papandreou Z, Peaslee D, Phaisangittisakul N, Prakhov S, Price JW, Pulver M, Ramirez AF, Sadler ME, Shafi A, Spinka H, Stanislaus S, Starostin A, Supek I, Staudenmaier HM, and Tippens WB

Abstract

Data are presented for the reaction pi(-)p-->pi(0)pi(0)n in the range from threshold to p(pi(-))=750 MeV/c. The systematics of the data and multipole analyses are examined for sensitivity to a f(0)(600) ("sigma") meson. A one-pion-exchange mechanism is found to be very weak, or absent. The reaction appears to become dominated by sequential pi(0) decays through the Delta(1232) resonance as the beam momentum increases, along with substantial interference effects from several competing mechanisms.

Published
2003
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3. Properties of the Lambda(1670)(1-)/2 resonance.

Author

Manley DM, Abaev VV, Allgower CE, Bekrenev V, Briscoe WJ, Clajus M, Comfort JR, Craig K, Grosnick D, Isenhower D, Knecht N, Koetke DD, Kulbardis AA, Kozlenko NG, Kruglov S, Lolos G, Lopatin IV, Manweiler R, Marusić A, McDonald S, Nefkens BM, Olmsted J, Papandreou Z, Peaslee DC, Phaisangittisakul N, Prakhov S, Price JW, Ramirez AF, Sadler M, Shafi A, Spinka H, Stanislaus TD, Starostin A, Staudenmaier HM, Strakovsky II, Supek I, and Tippens WB

Abstract

Recently the Crystal Ball Collaboration measured precise new data for the near-threshold reaction K(-)p-->etaLambda, which is dominated by formation of the Lambda(1670)1 / 2(-). In this Letter, we present results of a unitary, multichannel analysis that incorporates the new Crystal Ball data. For our preferred fit, we obtain mass M = 1673+/-2 MeV, width Gamma = 23+/-6 MeV, and elasticity x = 0.37+/-0.07. This elasticity is significantly larger than previously recognized. Resonance parameters of our preferred fit are in striking agreement with the quark-model predictions of Koniuk and Isgur.

Published
2002
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4. Determination of the quadratic slope parameter in eta-->3pi(0) decay.

Author

Tippens WB, Prakhov S, Allgower CE, Bekrenev V, Berger E, Briscoe WJ, Clajus M, Comfort JR, Craig K, Efendiev A, Grosnick D, Holstein BR, Huber GM, Isenhower D, Knecht N, Koetke D, Koulbardis A, Kozlenko N, Kruglov S, Lolos GJ, Lopatin I, Manley DM, Marusić A, Manweiler R, McDonald S, Nefkens BM, Olmsted J, Papandreou Z, Phaisangittisakul N, Price JW, Pulver M, Ramirez AF, Sadler ME, Shafi A, Spinka H, Stanislaus S, Starostin A, and Staudenmaier HM

Abstract

We have determined the quadratic slope parameter alpha for eta-->3pi(0) to be alpha = -0.031(4) from a 99% pure sample of 10(6)eta-->3pi(0) decays produced in the reaction pi(-)p-->n(eta) close to the eta threshold using the Crystal Ball detector at the AGS. The result is four times more precise than the present world data and disagrees with current chiral perturbation theory calculations by about four standard deviations.

Published
2001
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5. Search for quadrupole strength in the electroexcitation of the delta+(1232).

Author

Mertz C, Vellidis CE, Alarcon R, Barkhuff DH, Bernstein AM, Bertozzi W, Burkert V, Chen J, Comfort JR, Dodson G, Dolfini S, Dow K, Farkhondeh M, Finn JM, Gilad S, Gothe RW, Jiang X, Joo K, Kaloskamis NI, Karabarbounis A, Kelly JJ, Kowalski S, Kunz C, Lourie RW, McIntyre JI, Milbrath BD, Miskimen R, Mitchell JH, Papanicolas CN, Perdrisat CF, Sarty AJ, Shaw J, Soong SB, Tieger D, Tschalaer C, Turchinetz W, Ulmer PE, Van Verst S, Warren GA, Weinstein LB, Williamson S, Woo RJ, and Young A

Abstract

High-precision 1H(e,e'p)pi(0) measurements at Q2 = 0.126 (GeV/c)2 are reported, which allow the determination of quadrupole amplitudes in the gamma*N-->Delta transition; they simultaneously test the reliability of electroproduction models. The derived quadrupole-to-dipole ( I = 3/2) amplitude ratios, R(SM) = (-6.5+/-0.2(stat+sys)+/-2.5(mod))% and R(EM) = (-2.1+/-0.2(stat+sys)+/-2.0(mod))%, are dominated by model error. Previous R(SM) and R(EM) results should be reconsidered after the model uncertainties associated with the method of their extraction are taken into account.

Published
2001
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6. Measurement of pi(0)pi(0) production in the nuclear medium by pi(-) interactions at 0.408 GeV/c.

Author

Starostin A, Staudenmaier HM, Allgower CE, Bekrenev V, Berger E, Briscoe WJ, Clajus M, Comfort JR, Craig K, Grosnick D, Isenhower D, Knecht N, Koetke D, Koulbardis A, Kozlenko N, Kruglov S, Kycia T, Lolos G, Lopatin I, Manley DM, Manweiler B, Marusić A, McDonald S, Nefkens BM, Olmsted J, Papandreou Z, Peaslee D, Peterson RJ, Phaisangittisakul N, Prakhov S, Pulver M, Ramirez AF, Sadler M, Shafi A, Slaus I, Spinka H, Stanislaus S, Supek I, and Tippens WB

Abstract

We report on an investigation of the (pi(-),pi(0)pi(0)) reaction by means of measurements of the pi(0)pi(0) invariant mass distributions from pi(-) interactions on H, D, C, Al, and Cu targets at p(pi(-)) = 0.408 GeV/c. The sharp, strong peak in the pi(+)pi(-) invariant mass near 2m(pi) reported by the CHAOS Collaboration is not seen in our pi(0)pi(0) data. However, we do observe a change in the shape of the pi(0)pi(0) invariant mass spectrum for the different targets, indicating that the pi(0)pi(0) interaction diminishes in the nuclear medium as represented by nuclei D, C, Al, and Cu, compared to hydrogen.

Published
2000
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7. Search for the CP forbidden decay eta-->4pi(0)

Author

Prakhov S, Tippens WB, Allgower C, Bekrenev V V, Berger E, Briscoe WJ, Clajus M, Comfort JR, Craig K, Grosnick D, Huber GM, Isenhower D, Knecht N, Koetke D, Koulbardis A, Kozlenko N, Kruglov S, Kycia T, Lolos GJ, Lopatin I I, Manley DM, Marusic A, Manweiler R, McDonald S, Nefkens BM, and Olmsted J

Abstract

We report the first determination of the upper limit for the branching ratio of the CP forbidden decay eta-->4pi(0). No events were observed in a sample of 3.0x10(7) eta decays. The experiment was performed with the Crystal Ball multiphoton spectrometer installed in a separated pi(-) beam at the AGS (Alternating Gradient Synchrotron). At the 90% confidence limit, B(eta-->4pi(0))

Published
2000
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8. Analyzing powers for pion charge exchange on polarized 13C.

Author

Görgen JJ, Comfort JR, Tinsley JR, Averett T, DeKorse J, Franklin B, Ritchie BG, Kyle G, Klein A, Berman B, Burleson G, Cranston K, Faucett JA, Jarmer JJ, Knudson JN, Penttilä S, Tanaka N, Brinkmöller B, Dehnhard D, Yen YF, Hoibråten S, Breuer H, Flanders BS, Khandaker MA, Naples DL, Zhang D, Barlett ML, Hoffmann GW, and Purcell M

Published
1991
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9. Asymmetry measurement of pion elastic scattering from polarized 13C in the energy region of the P33 resonance.

Author

Yen YF, Brinkmöller B, Dehnhard D, Sterbenz SM, Yu YJ, Berman B, Burleson GR, Cranston K, Klein A, Kyle GS, Alarcon R, Averett T, Comfort JR, Görgen JJ, Ritchie BG, Tinsley JR, Barlett M, Hoffmann GW, Johnson K, Moore CF, Purcell M, Ward H, Williams A, Faucett JA, Greene SJ, Jarmer JJ, McGill JA, Morris CL, Penttilä S, Tanaka N, Fortune HT, Insko E, Ivie R, O'Donnell JM, Smith D, Khandaker MA, and Chakravarti S

Published
1991
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10. Neutron deformation in 165Ho.

Author

Knudson JN, Bowman JD, Penttilä SI, Comfort JR, Ritchie BG, Goergen J, Mathis D, Tinsley J, Hanna SS, King B, Pocanic D, Loveman RA, Fritz LS, and Dixon NS

Published
1991
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