Browsing by Author "Jahn R."

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    A precision determination of the mass of the η meson
    (2005-07-21) Abdel-Bary M.; Budzanowski A.; Chatterjee A.; Ernst J.; Hawranek P.; Jahn R.; Jha V.; Kilian K.; Kliczewski S.; Kirillov D.; Kolev D.; Kravcikova M.; Kutsarova T.; Lesiak M.; Lieb J.; Machner H.; Magiera A.; Maier R.; Martinska G.; Nedev S.; Piskunov N.; Prasuhn D.; Protić D.; Von Rossen P.; Roy B.J.; Sitnik I.; Siudak R.; Smiechowicz M.; Stein H.J.; Tsenov R.; Ulicny M.; Urban J.; Vankova G.; Wilkin C.
    Several processes of meson production in proton-deuteron collisions have been measured simultaneously using a calibrated magnetic spectrograph. Among these processes, the η meson is seen clearly as a sharp missing-mass peak on a slowly varying background in the p+d→He3+X reaction. Knowing the kinematics of the other reactions with well determined masses, it is possible to deduce a precise mass for the η meson. The final result, m(η)=547.311±0.028(stat)±0.032(syst)MeV/c2, is significantly lower than that found by the recent NA48 measurement, though it is consistent with values obtained in earlier counter experiments. © 2005 Elsevier B.V. All rights reserved.
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    Cross section and tensor analysing power of the d d → η α reaction near threshold
    (2009-04-15) Budzanowski A.; Chatterjee A.; Gebel R.; Hawranek P.; Jahn R.; Jha V.; Kilian K.; Kliczewski S.; Kirillov D.; Kirillov D.; Kolev D.; Kravcikova M.; Lesiak M.; Lieb J.; Machner H.; Magiera A.; Maier R.; Martinska G.; Nedev S.; Piskunov N.; Prasuhn D.; Protić D.; Ritman J.; von Rossen P.; Roy B.J.; Sitnik I.; Siudak R.; Tsenov R.; Urban J.; Vankova G.; Wilkin C.
    The angular distributions of the unpolarised differential cross section and tensor analysing power Ax x of the over(d, →) d → α η reaction have been measured at an excess energy of 16.6 MeV. The ambiguities in the partial-wave description of these data are made explicit by using the invariant amplitude decomposition. This allows the magnitude of the s-wave amplitude to be extracted and compared with results published at lower energies. In this way, firmer bounds could be obtained on the scattering length of the ηα system. The results do not, however, unambiguously prove the existence of a quasi-bound ηα state. © 2009 Elsevier B.V. All rights reserved.
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    Search for η-mesic nuclei in a recoil-free transfer reaction
    (2009-01-05) Budzanowski A.; Chatterjee A.; Hawranek P.; Jahn R.; Jain B.K.; Jha V.; Kailas S.; Kilian K.; Kliczewski S.; Kirillov D.; Kirillov D.; Kolev D.; Kravcikova M.; Lesiak M.; Lieb J.; Liu L.C.; MacHner H.; Magiera A.; Maier R.; Martinska G.; Nedev S.; Piskunov N.; Protić D.; Ritman J.; Von Rossen P.; Roy B.J.; Shukla P.; Sitnik I.; Siudak R.; Tsenov R.; Urban J.; Vankova G.
    We have studied the reaction p+Al27 → He3+p+π-+X at recoil-free kinematics. An η meson possibly produced in this reaction would be thus almost at rest in the laboratory system and could therefore be bound with high probability, if nuclear η states exist. The decay of such a state through the N*(1535) resonance would lead to a proton-π- pair emitted in opposite directions. For these conditions we find some indication of such a bound state. An upper limit of ≈0.5 nb is found. © 2009 The American Physical Society.