A. Starostin

Publications (65)78.62 Total impact

• Article: Measurement of the beam-helicity asymmetry $I^{\odot}$ in the photoproduction of $\pi^0$-pairs off the proton and off the neutron

  M. Oberle, B. Krusche, J. Ahrens, J. R. M. Annand, H. J. Arends, K. Bantawa, P. A. Bartolome, R. Beck, V. Bekrenev, H. Berghaeuser, [......], D. I. Sober, A. Starostin, I. Supek, M. Thiel, A. Thomas, M. Unverzagt, D. P. Watts, D. Werthmueller, L. Witthauer, F. Zehr
  [show abstract] [hide abstract]
  ABSTRACT: Beam-helicity asymmetries have been measured at the MAMI accelerator in Mainz for the photoproduction of neutral pion pairs in the reactions $\vec{\gamma}p\rightarrow p\pi^0\pi^0$ and $\vec{\gamma}d\rightarrow (n)p\pi^0\pi^0$, $\vec{\gamma}d\rightarrow (p)n\pi^0\pi^0$ off free protons and off quasi-free nucleons bound in the deuteron for incident photon energies up to 1.4 GeV. Circularly polarized photons were produced from bremsstrahlung of longitudinally polarized electrons and tagged with the Glasgow magnetic spectrometer. Decay photons from the $\pi^0$ mesons, recoil protons, and recoil neutrons were detected in the 4$\pi$ covering electromagnetic calorimeter composed of the Crystal Ball and TAPS detectors. After kinematic reconstruction of the final state, excellent agreement was found between the results for free and quasi-free protons. This demonstrates that the free-nucleon behavior of such observables can be extracted from measurements with quasi-free nucleons, which is the only possibility for the neutron. Contrary to expectations, the measured asymmetries are very similar for reactions off protons and neutrons. The results are compared to the predictions from the Two-Pion-MAID reaction model and (for the proton) also to the Bonn-Gatchina coupled channel analysis.
  04/2013;
• Article: Coherent photoproduction of pi^0- and eta-mesons off 7Li

  Y. Maghrbi, B. Krusche, J. Ahrens, J. R. M. Annand, H. J. Arends, R. Beck, V. Bekrenev, B. Boillat, A. Braghieri, D. Branford, [......], S. Schumann, D. Sober, A. Starostin, I. Supek, C. M. Tarbert, A. Thomas, M. Unverzagt, D. P. Watts, D. Werthmueller, F. Zehr
  [show abstract] [hide abstract]
  ABSTRACT: Coherent photoproduction of $\pi^0$-mesons from threshold ($E_{th} \approx$ 136 MeV) throughout the $\Delta$-resonance region and of $\eta$-mesons close to the production threshold ($E_{th} \approx$ 570 MeV for $\eta$) has been measured for $^7$Li nuclei. The experiment was performed using the tagged-photon beam of the Mainz MAMI accelerator with the Crystal Ball and TAPS detectors combined to give an almost 4$\pi$ solid-angle electromagnetic calorimeter. The reactions were identified by a combined invariant-mass and missing-energy analysis. A comparison of the pion data to plane-wave impulse modelling tests the nuclear mass form factor. So far coherent $\eta$-production had been only identified for the lightest nuclear systems ($^2$H and $^3$He). For $^3$He a large enhancement of the cross section above plane-wave approximations had been reported, indicating the formation of a quasi-bound state. The present Li-data for $\eta$-production agree with a plane-wave approximation. Contrary to $^3$He, neither a threshold enhancement of the total cross section nor a deviation of the angular distributions from the expected form-factor dependence were observed.
  03/2013;
• Article: Accurate Test of Chiral Dynamics in the \boldmath$\vec{\gamma} p \rightarrow \pi^0p$ Reaction

  D. Hornidge, P. Aguar Bartolome, J. R. M. Annand, H. J. Arends, R. Beck, V. Bekrenev, H. Berghaeuser, A. M. Bernstein, A. Braghieri, W. J. Briscoe, [......], M. H. Sikora, A. Starostin, I. Supek, M. Thiel, A. Thomas, L. Tiator, M. Unverzagt, D. P. Watts, D. Werthmueller, L. Witthauer
  [show abstract] [hide abstract]
  ABSTRACT: A precision measurement of the differential cross sections $d\sigma/d\Omega$ and the linearly polarized photon asymmetry $\Sigma \equiv \left(d\sigma_\perp - d\sigma_\parallel \right) \slash \left(d\sigma_\perp + d\sigma_\parallel \right)$ for the $\vec{\gamma} p \rightarrow \pi^0p$ reaction in the near-threshold region has been performed with a tagged photon beam and almost $4\pi$ detector at the Mainz Microtron. The Glasgow-Mainz photon tagging facility along with the Crystal Ball/TAPS multi-photon detector system and a cryogenic liquid hydrogen target were used. These data allowed for a precise determination of the energy dependence of the real parts of the $S$- and all three $P$-wave amplitudes for the first time and provide the most stringent test to date of the predictions of Chiral Perturbation Theory and its energy region of agreement with experiment.
  11/2012;
• Article: Determination of the {\eta} mass with the Crystal Ball at MAMI-B

  A. Nikolaev, P. Aguar-Bartolomé, J. Ahrens, J. R. M. Annand, H. J. Arends, R. Beck, V. Bekrenev, B. Boillat, A. Braghieri, D. Branford, [......], S. Schumann, D. Sober, A. Starostin, I. Supek, C. M. Tarbert, A. Thomas, M. Unverzagt, Th. Walcher, D. P. Watts, F. Zehr
  [show abstract] [hide abstract]
  ABSTRACT: A new precise determination of the {\eta} meson mass is presented. It is based on a measurement of the threshold for the {\gamma}p -> p{\eta} reaction using the tagger focal-plane microscope detector at the MAMI-B facility in Mainz. The tagger microscope has a higher energy resolution than the standard tagging spectrometer and, hence, allowed an improvement in the accuracy compared to the previous {\eta} mass measurement at MAMI-B. The result m{\eta} = (547.851 +- 0.031 stat. +- 0.062 syst.) MeV agrees very well with the precise values of the NA48, KLOE and CLEO collaborations and deviates by about 5{\sigma} from the smaller, but also very precise value obtained by the GEM collaboration at COSY.
  07/2012;
• Article: Photoproduction of pi0pi0 and pi0pi+-pairs off the proton from threshold to the second resonance region

  F. Zehr, B. Krusche, P. Aguar, J. Ahrens, J. R. M. Annand, H. J. Arends, R. Beck, V. Bekrenev, B. Boillat, A. Braghieri, [......], T. Rostomyan, S. Schumann, D. Sober, A. Starostin, I. Supek, C. M. Tarbert, A. Thomas, M. Unverzagt, Th. Walcher, D. P. Watts
  [show abstract] [hide abstract]
  ABSTRACT: Precise total cross-sections and invariant-mass distributions have been measured for photoproduction of pion pairs off the proton producing $p\pi^0\pi^0$ and $n\pi^+\pi^0$ final states from the threshold region up to 800 MeV incident photon energy. Additionally, beam helicity asymmetries have been measured in the second resonance region (550 MeV - 820 MeV). The experiment was performed at the tagged photon beam of the Mainz MAMI accelerator with the Crystal Ball and TAPS detectors combined to give an almost 4$\pi$ solid-angle electromagnetic calorimeter. The results are much more precise than any previous measurements and confirm the chiral perturbation theory predictions for the threshold behavior of these reactions. In the second resonance region, the invariant-mass distributions of meson-meson and meson-nucleon pairs are in reasonable agreement with model predictions, but none of the models reproduce the asymmetries for the mixed-charge channel.
  07/2012;
• Article: Study of the gamma p --> pi0 pi0 p reaction with the Crystal Ball/TAPS at the Mainz

  V. L. Kashevarov, A. Fix, S. Prakhov, P. Aguar-Bartolomé, J. R. M. Annand, H. J. Arends, K. Bantawa, R. Beck, V. Bekrenev, H. Berghäuser, [......], I. I. Strakovsky, I. M. Suarez, I. Supek, C. M. Tarbert, M. Thiel, A. Thomas, M. Unverzagt, D. P. Watts, D. Werthmüller, F. Zehr
  [show abstract] [hide abstract]
  ABSTRACT: The gamma p --> pi0 pi0 p reaction has been measured from threshold to 1.4 GeV using the Crystal Ball and TAPS photon spectrometers together with the photon tagging facility at the Mainz Microtron. The experimental results include total and differential cross sections as well as specific angular distributions, which were used to extract partial-wave amplitudes. In particular, the energy region below the D13(1520) resonance was studied.
  04/2012;
• Source

  Available from: W. J. Briscoe

  Article: Photoproduction of on protons and the (1700)D33 -resonance

  The Crystal Ball at MAMI, TAPS, and Collaborations, V. L. Kashevarov, A. Fix, P. Aguar-Bartolomé, L. K. Akasoy, J. R. M. Annand, H. J. Arends, K. Bantawa, R. Beck, V. Bekrenev, [......], A. Starostin, I. M. Suarez, I. Supek, C. M. Tarbert, M. Thiel, A. Thomas, M. Unverzagt, D. P. Watts, I. Zamboni, F. Zehr
  [show abstract] [hide abstract]
  ABSTRACT: Total and differential cross-sections for the reaction gp®p0hp\ensuremath \gamma p\rightarrow\pi^0\eta p have been measured with the Crystal Ball/TAPS detector using the tagged photon facility at the MAMI C accelerator in Mainz. In the energy range Eg = 0.95-1.4\ensuremath E_{\gamma} = 0.95\mbox{--}1.4 GeV the reaction is dominated by the excitation and sequential decay of the D(1700)D33\ensuremath \Delta(1700)D_{33} -resonance. Angular distributions measured with high statistics allow us to determine the ratio of hadronic decay widths GhD/GpS11\ensuremath \Gamma_{\eta\Delta}/\Gamma_{\pi S_{11}} and the ratio of the helicity amplitudes A3/2/A1/2\ensuremath A_{3/2}/A_{1/2} for this resonance.
  European Physical Journal A 04/2012; 42(2):141-149. · 2.19 Impact Factor
• Source

  Available from: W. J. Briscoe

  Article: Radiative π0 photoproduction on protons in the Δ+ (1232) region

  TAPS and Collaborations The Crystal Ball at MAMI, S. Schumann, B. Boillat, E. J. Downie, P. Aguar-Bartolomé, J. Ahrens, J. R. M. Annand, H. J. Arends, R. Beck, V. Bekrenev, [......], T. Rostomyan, D. Sober, A. Starostin, I. Supek, C. M. Tarbert, A. Thomas, M. Unverzagt, Th. Walcher, D. P. Watts, F. Zehr
  [show abstract] [hide abstract]
  ABSTRACT: The reaction γp → pπ 0γ′ has been measured with the Crystal Ball/TAPS detectors using the energy-tagged photon beam at the electron accelerator facility MAMI-B. Energy and angular differential cross-sections for the emitted photon γ′ and angular differential cross-sections for the π0 have been determined with high statistics in the energy range of the Δ+ (1232)-resonance. Cross-sections and the ratio of the cross-section to the nonradiative process γp → pπ 0 are compared to theoretical reaction models, having the anomalous magnetic moment κ Δ as free parameter. As the shape of the experimental distributions is not reproduced in detail by the model calculations, currently no extraction of κ Δ is feasible.
  European Physical Journal A 04/2012; 43(3):269-282. · 2.19 Impact Factor
• Source

  Available from: W. J. Briscoe

  Article: Coherent photoproduction of eta-mesons off 3He - search for eta-mesic nuclei

  F. Pheron, J. Ahrens, J. R. M. Annand, H. J. Arends, K. Bantawa, P. A. Bartolome, R. Beck, V. Bekrenev, H. Berghaeuser, B. Boillat, [......], D. I. Sober, A. Starostin, I. Supek, M. Thiel, A. Thomas, M. Unverzagt, D. P. Watts, D. Werthmueller, L. Witthauer, F. Zehr
  [show abstract] [hide abstract]
  ABSTRACT: Coherent photoproduction of $\eta$-mesons off $^3$He, i.e. the reaction $\gamma ^3{He}\rightarrow \eta ^3{He}$, has been investigated in the near-threshold region. The experiment was performed at the Glasgow tagged photon facility of the Mainz MAMI accelerator with the combined Crystal Ball - TAPS detector. Angular distributions and the total cross section were measured using the $\eta\rightarrow \gamma\gamma$ and $\eta\rightarrow 3\pi^0\rightarrow 6\gamma$ decay channels. The observed extremely sharp rise of the cross section at threshold and the behavior of the angular distributions are evidence for a strong $\eta {^3{He}}$ final state interaction, pointing to the existence of a resonant state. The search for further evidence of this state in the excitation function of $\pi^0$-proton back-to-back emission in the $\gamma ^3{He}\rightarrow \pi^0 pX$ reaction revealed a very complicated structure of the background and could not support previous conclusions.
  01/2012;
• Article: Erratum: Experimental study of the γp→ηp reaction with the Crystal Ball detector at the Mainz Microtron (MAMI-C) [Phys. Rev. C 82, 035208 (2010)]

  E. F. McNicoll, S. Prakhov, I. I. Strakovsky, P. Aguar-Bartolomé, L. K. Akasoy, J. R. M. Annand, H. J. Arends, R. A. Arndt, Ya. I. Azimov, K. Bantawa, [......], I. Supek, M. Thiel, A. Thomas, L. Tiator, M. Unverzagt, D. P. Watts, D. Werthmüller, R. L. Workman, I. Zamboni, F. Zehr
  [show abstract] [hide abstract]
  ABSTRACT: Here we correct a factor of 2 missed in one of figures and the corresponding sentence in the text. It does not change any conclusions.
  Physical Review C 07/2011; 84(2):29901. · 3.31 Impact Factor
• Source

  Available from: W. J. Briscoe

  Article: Measurement of 3pi^0 photoproduction on the proton from threshold to 1.4 GeV

  A. Starostin, I. M. Suarez, B. M. K. Nefkens, J. Ahrens, J. R. M. Annand, H.J. Arends, K. Bantawa, P. A. Bartolome, R. Beck, V. Bekrenev, [......], S. Schumann, M. H. Sikora, D. Sober, I. Supek, M. Thiel, A Thomas, M. Unverzagt, D. P. Watts, D. Wertmueller, L. Witthauer
  [show abstract] [hide abstract]
  ABSTRACT: The total cross section for gamma p -> 3pi0 p has been measured for the first time from threshold to 1.4 GeV using the tagged photon beam of the Mainz Microtron. The equipment utilized the Crystal Ball multiphoton spectrometer, the TAPS forward detector and a particle identification detector. The gamma p -> 3pi0 p total cross section has two broad enhancements at sqrt{s}~1.5 GeV and 1.7 GeV. We obtained the ratio of the total cross sections gamma p -> 3pi0 p to gamma p -> eta p equal to 0.014 \pm 0.001 at sqrt{s}~1.5 GeV.
  01/2011;
• Source

  Available from: W. J. Briscoe

  Article: First measurement of the circular beam asymmetry in the gamma p --> pi0 eta p reaction

  V. L. Kashevarov, A. Fix, P. Aguar-Bartolomé, L. K. Akasoy, J. R. M. Annand, H.J. Arends, K. Bantawa, R. Beck, V. Bekrenev, H. Berghäuser, [......], I. M. Suarez, I. Supek, C. Tarbert, M. Thiel, A Thomas, M. Unverzagt, D. P. Watts, D. Werthmüller, I. Zamboni, F. Zehr
  [show abstract] [hide abstract]
  ABSTRACT: The circular photon asymmetry for pi0 eta photoproduction on the proton was measured for the first time at the tagged photon facility of the MAMI C accelerator using the Crystal Ball/TAPS photon spectrometer. The experimental results are interpreted within a phenomenological isobar model that confirms the dominant role of the Delta(1700)D33 resonance. The measured asymmetry allows us to identify small contributions from positive-parity resonances via interference terms with the dominant D33 amplitude. Comment: 11 pages, 3 figures, submitted to Phys.Lett. B
  09/2010;
• Source

  Available from: Mark Paris

  Article: Study of the gp-->etap reaction with the Crystal Ball detector at the Mainz Microtron(MAMI-C)

  E. F. McNicoll, S. Prakhov, I. I. Strakovsky, P. Aguar-Bartolomepmainz, L. K. Akasoy, J. R. M. Annand, H.J. Arends, R. A. Arndt, Ya. I. Azimov, K. Bantawa, [......], I. Supek, M. Thiel, A Thomas, L. Tiator, M. Unverzagt, D. P. Watts, D. Werthmueller, R. L. Workman, I. Zamboni, F. Zehr
  [show abstract] [hide abstract]
  ABSTRACT: The gp-->etap reaction has been measured with the Crystal Ball and TAPS multiphoton spectrometers in the energy range from the production threshold of 707 MeV to 1.4 GeV (1.49 =< W >= 1.87 GeV). Bremsstrahlung photons produced by the 1.5-GeV electron beam of the Mainz Microtron MAMI-C and momentum analyzed by the Glasgow Tagging Spectrometer were used for the eta-meson production. Our accumulation of 3.8 x 10^6 gp-->etap-->3pi0p-->6gp events allows a detailed study of the reaction dynamics. The gp-->etap differential cross sections were determined for 120 energy bins and the full range of the production angles. Our data show a dip near W = 1680 MeV in the total cross section caused by a substantial dip in eta production at forward angles. The data are compared to predictions of previous SAID and MAID partial-wave analyses and to thelatest SAID and MAID fits that have included our data. Comment: 15 pages, 12 figures
  07/2010;
• Source

  Available from: W. J. Briscoe

  Article: Radiative pi0 photoproduction on protons in the Delta+(1232) region

  S. Schumann, B Boillat, E. J. Downie, P. Aguar-Bartolomé, J. Ahrens, J. R. M. Annand, H.J. Arends, R. Beck, V. Bekrenev, A. Braghieri, [......], T. Rostomyan, D. Sober, A. Starostin, I. Supek, C. M. Tarbert, A Thomas, M. Unverzagt, Th. Walcher, D. P. Watts, F. Zehr
  [show abstract] [hide abstract]
  ABSTRACT: The reaction gamma p -> p pi0 gamma' has been measured with the Crystal Ball / TAPS detectors using the energy-tagged photon beam at the electron accelerator facility MAMI-B. Energy and angular differential cross sections for the emitted photon gamma' and angular differential cross sections for the pi0 have been determined with high statistics in the energy range of the Delta+(1232) resonance. Cross sections and the ratio of the cross section to the non-radiative process gamma p -> p pi0 are compared to theoretical reaction models, having the anomalous magnetic moment kappa_Delta+ as free parameter. As the shape of the experimental distributions is not reproduced in detail by the model calculations, currently no extraction of kappa_Delta+ is feasible. Comment: 14 pages, 19 figures
  01/2010;
• Source

  Available from: J. Ryckebusch

  Article: Measurement of $K^- p$ radiative capture to $\gamma \Lambda$ and $\gamma \Sigma^0$ for $p_{K^-}$ between 514 and 750 MeV/$c$

  S. Prakhov, P. Vancraeyveld, N Phaisangittisakul, B. M. K. Nefkens, V. Bekrenev, W. J. Briscoe, L. De Cruz, D Isenhower, N. Knecht, A Koulbardis, [......], D. Peaslee, J W Price, J. Ryckebusch, M. Sadler, A Shafi, A. Starostin, H. M. Staudenmaier, I. I. Strakovsky, I. Supek, T. Van Cauteren
  [show abstract] [hide abstract]
  ABSTRACT: Differential cross sections for $K^-$ radiative capture in flight on the proton, leading to the $\gamma\Lambda$ and $\gamma\Sigma^0$ final states, have been measured at eight $K^-$ momenta between 514 and 750 MeV/$c$. The data were obtained with the Crystal Ball multiphoton spectrometer installed at the separated $K/\pi$ beam line C6 of the BNL Alternating Gradient Synchrotron. The results substantially improve the existing experimental data available for studying radiative decays of excited hyperon states. An exploratory theoretical analysis is performed within the Regge-plus-resonance approach. According to this analysis, the $\gamma\Sigma^0$ final state is dominated by hyperonresonance exchange and hints at an important role for a resonance in the mass region of 1700 MeV. In the $\gamma\Lambda$ final state, on the other hand, the resonant contributions account for only half the strength, and the data suggest the importance of a resonance in the mass region of 1550 MeV.
  12/2009;
• Source

  Available from: W. J. Briscoe

  Article: Differential cross sections of the charge-exchange reaction pi- p --> pi0 n in the momentum range from 103 to 178 MeV/c

  D. Mekterović, I. Supek, V. Abaev, V. Bekrenev, C. Bircher, W. J. Briscoe, R. V. Cadman, M. Clajus, J.R. Comfort, K Craig, [......], A. Ramirez, M E Sadler, A Shafi, H Spinka, S Stanislaus, A. Starostin, H. M. Staudenmaier, I. Strakovsky, W B Tippens, S. Watson
  [show abstract] [hide abstract]
  ABSTRACT: Measured values of the differential cross sections for pion-nucleon charge exchange, pi- p --> pi0 n, are presented for pi- momenta of 103, 112, 120, 130, 139, 152, and 178 MeV/c. Complete angular distributions were obtained by using the Crystal Ball detector at the Alternating Gradient Synchrotron at Brookhaven National Laboratory. Statistical uncertainties of the differential cross sections vary from 3% to 6% in the backward angle region, and from 6% to about 20% in the forward region with the exception of the two most forward angles. The systematic uncertainties are estimated to be about 3% for all momenta. Comment: 18 pages, 12 figures, submitted to Phys. Rev. C
  08/2009;
• Source

  Available from: W. J. Briscoe

  Article: Beam-helicity asymmetries in double-pion photoproduction off the proton.

  D Krambrich, F Zehr, A Fix, L Roca, P Aguar, J Ahrens, J R M Annand, H J Arends, R Beck, V Bekrenev, [......], T Rostomyan, S Schumann, D Sober, A Starostin, I Supek, C M Tarbert, A Thomas, M Unverzagt, Th Walcher, D P Watts
  [show abstract] [hide abstract]
  ABSTRACT: Beam-helicity asymmetries have been measured at the MAMI accelerator in Mainz in the three isospin channels gamma[over -->]p-->pi(+)pi(0)n, gamma[over -->]p-->pi(0)pi(0)p, and gamma[over -->]p-->pi(+)pi(-)p. The circularly polarized photons, produced from bremsstrahlung of longitudinally polarized electrons, were tagged with the Glasgow magnetic spectrometer. Charged pions and the decay photons of pi(0) mesons were detected in a 4pi electromagnetic calorimeter which combined the Crystal Ball detector with the TAPS detector. The precisely measured asymmetries are very sensitive to details of the production processes and are thus key observables in the modeling of the reaction dynamics.
  Physical Review Letters 07/2009; 103(5):052002. · 7.37 Impact Factor
• Article: Search for the charge-conjugation-forbidden decay ω→ηπ0

  A. Starostin, B. M. K. Nefkens, J. Ahrens, J. R. M. Annand, H. J. Arends, K. Bantawa, P. A. Bartolome, R. Beck, V. Bekrenev, A. Braghieri, [......], S. Schumann, M. H. Sikora, D. Sober, I. M. Suarez, I. Supek, C. M. Tarbert, M. Thiel, A. Thomas, M. Unverzagt, D. P. Watts
  [show abstract] [hide abstract]
  ABSTRACT: A new upper limit of 2.3×10-4 on the branching ratio of the decay ω→ηπ0 has been obtained using the Crystal Ball multiphoton spectrometer at the Mainz Microtron MAMI. This decay is forbidden by charge-conjugation invariance of the strong and electromagnetic interactions. We have also obtained the upper limit of 2.3×10-4 for the forbidden decay ω→3π0 and the upper limit of 2.4×10-4 for ω→2π0.
  Phys. Rev. C. 06/2009; 79(6).
• Source

  Available from: W. J. Briscoe

  Article: Precise measurement of the neutron magnetic form factor G(M)n in the few-GeV2 region.

  J Lachniet, A Afanasev, H Arenhövel, W K Brooks, G P Gilfoyle, D Higinbotham, S Jeschonnek, B Quinn, M F Vineyard, G Adams, [......], M Williams, E Wolin, M H Wood, A Yegneswaran, J Yun, M Yurov, L Zana, J Zhang, B Zhao, Z W Zhao
  [show abstract] [hide abstract]
  ABSTRACT: The neutron elastic magnetic form factor was extracted from quasielastic electron scattering on deuterium over the range Q;{2}=1.0-4.8 GeV2 with the CLAS detector at Jefferson Lab. High precision was achieved with a ratio technique and a simultaneous in situ calibration of the neutron detection efficiency. Neutrons were detected with electromagnetic calorimeters and time-of-flight scintillators at two beam energies. The dipole parametrization gives a good description of the data.
  Physical Review Letters 06/2009; 102(19):192001. · 7.37 Impact Factor
• Article: Measurement of direct f0(980) photoproduction on the proton.

  M Battaglieri, R De Vita, A P Szczepaniak, K P Adhikari, M Aghasyan, M J Amaryan, P Ambrozewicz, M Anghinolfi, G Asryan, H Avakian, [......], D P Weygand, M Williams, E Wolin, M H Wood, A Yegneswaran, M Yurov, L Zana, J Zhang, B Zhao, Z W Zhao
  [show abstract] [hide abstract]
  ABSTRACT: We report on the results of the first measurement of exclusive f_{0}(980) meson photoproduction on protons for E_{gamma}=3.0-3.8 GeV and -t=0.4-1.0 GeV2. Data were collected with the CLAS detector at the Thomas Jefferson National Accelerator Facility. The resonance was detected via its decay in the pi;{+}pi;{-} channel by performing a partial wave analysis of the reaction gammap-->ppi;{+}pi;{-}. Clear evidence of the f_{0}(980) meson was found in the interference between P and S waves at M_{pi;{+}pi;{-}} approximately 1 GeV. The S-wave differential cross section integrated in the mass range of the f_{0}(980) was found to be a factor of about 50 smaller than the cross section for the rho meson. This is the first time the f_{0}(980) meson has been measured in a photoproduction experiment.
  Physical Review Letters 04/2009; 102(10):102001. · 7.37 Impact Factor