BEGIN:VCALENDAR
VERSION:2.0
PRODID:-//CERN//INDICO//EN
BEGIN:VEVENT
SUMMARY:STUDY OF 6He – 4He SCATTERING AT THE ACCULINNA-2 FRAGMENT SEPARA
 TOR
DTSTART;VALUE=DATE-TIME:20261027T162500Z
DTEND;VALUE=DATE-TIME:20261027T163000Z
DTSTAMP;VALUE=DATE-TIME:20261022T163058Z
UID:indico-contribution-6505@cern.ch
DESCRIPTION:Speakers: Danila Makarov (Flerov Laboratory of Nuclear Reactio
 ns\, JINR\, Dubna\, Russia\; National Research Nuclear University MEPhI\, 
 Moscow\, Russia)\nThis work presents the results of an experiment performe
 d at the ACCULINNA-2 fragment separator (FLNR JINR) aimed at studying the 
 elastic and inelastic scattering of ^{6}He + ^{4}He over a wide angular ra
 nge. A secondary 6He beam with an energy of 151 (168) MeV irradiated a 5.5
 -mm thick cryogenic gaseous ^{4}He target maintained at a temperature of 1
 2 K and a pressure of 1 (2) atm. The reaction products were registered in 
 a two-arm geometry using the detector system described in [1].\nThe primar
 y objective of the investigation was to determine the differential cross s
 ections for the ^{6}He + ^{4}He → ^{4}He + ^{6}He(g.s.) and ^{6}He + ^{4
 }He → ^{4}He + ^{6}He(2+) channels. For the channel populating the groun
 d state of 6He\, the angular distribution in the center-of-mass system (c.
 m.s.) was obtained across a wider angular range and with better resolution
  than in previous measurements [2]. In particular\, new data were obtained
  for Θ_{c.m.s.} ~ 15°–60° and\, most notably\, for the Θ_{c.m.s.} ~ 
 130°–165° range\, which corresponds to the two-neutron transfer reacti
 on mechanism. The angular distribution for the channel involving the excit
 ation of the 6He(2^{+}) state was extracted by selecting events with the s
 imultaneous detection of two alpha particles. Consequently\, the angular d
 ependence of the cross section in the 130°–165° region was obtained fo
 r the first time. The optical model was applied to describe the data at fo
 rward angles\, whereas the FRESCO and DWUCK5 codes were utilized for the b
 ackward angles.\nIn addition\, the spectrum of highly excited states of 6H
 e\, obtained via the missing mass method in the ^{6}He + ^{4}He → ^{4}He
  + ^{6}He* (^{4}He+n+n) reaction\, was analyzed separately. It is demonstr
 ated that this spectrum is formed by the contribution of a peak correspond
 ing to the 2^{+} state at E_{ex} = 1.8 MeV\, alongside a long "tail" most 
 likely attributed to negative parity states. In the ^{4}He–t coincidence
 s\, a peak presumably associated with the dipole mode was observed at E_{e
 x} = 26–27 MeV\, which is induced by the breakup of the alpha cluster in
  6He. The mechanism underlying the emergence of potential background event
 s at excitation energies of 15 MeV and above\, as well as methods for thei
 r elimination\, are discussed.\nReferences\n1. A. A. Bezbakh\, S. G. Belog
 urov\, V. Chudoba et al.\, Detector Array for the 7H Nucleus Multi-Neutron
  Decay Study\, Phys. Part. Nuclei Lett. 20\, 629–636 (2023).\n2. G. M. T
 er-Akopian\, A. M. Rodin\, A. S. Fomichev et al.\, Two-neutron exchange ob
 served in the ^{6}He+^{4}He reaction. Search for the "di-neutron" configur
 ation of 6He\, Phys. Lett. B 426\, 251–256 (1998).\n\nhttps://indico.par
 ticle.mephi.ru/event/626/contributions/6505/
LOCATION:Sevastopol hotel Conference Hall 1
URL:https://indico.particle.mephi.ru/event/626/contributions/6505/
END:VEVENT
END:VCALENDAR