Y. Maeda

Quasifree p(K-,K+)Xi- reaction in nuclear emulsion

Abstract A study of 1.66 GeV c K − beam induced ( K − ,K + ) reactions in the nuclear emulsion target is presented and 796 ( K − , K + ) reaction vertices ( p K + ⩾ 1 GeV /c ) containing 18 single hyperfragments are identified. There is no clear(spatially separated) double hyperfragment nor twin single hyperfragment in the identified 796 ( K − ,K + ) reactions. These events are classified and their characteristics are described in detail. In the region p K + ⩾ 1 GeV /c where the quasifree K − (p) → K + Ξ − is the dominant process, the probability of Ξ − emission from the reaction vertex is determined to be 73.9 −4.6 +4.5 %. From this value, the mean free path of Ξ − in a nucleus is estimated to be 4.7 −1.0 +1.5 fm for 〈p Ξ − 〉 ∼ 0.6 GeV /c by assuming a simple model of uniform nuclear matter.

Analysis of 303 GeV/c proton-nucleus interactions tagged by high-energy γ-rays with emulsion chambers

SummaryTwo emulsion chambers are exposed to 303 GeV/c proton beams at the Fermi National Accelerator Laboratory. The event structure of 70 proton-nucleus interactions tagged by high-energy γ-rays is analysed. Strong correlation is observed in the forward fragmentation region between high-energy γ-rays and a charged secondary particle with the highest transverse momentum (PT ≳ 1 GeV/c) in each event. Formation of a forward excited baryon and its decay into a charged baryon and γ-rays is one of the possible explanations of this effect. Correlation between the excited baryon and other produced particles in each interaction is also studied.RiassuntoSi espongono due camere di emulsione a raggi di protoni di 303 GeV/c al Laboratorio Nazionale dell’acceleratore E. Fermi. Si analizza la struttura dell’evento di 70 interazioni protone-nucleo dovute a raggi γ ad alta energia. Si osserva una forte correlazione nella regione di frammentazione in avanti tra raggi γ ad alta energia e una particella secondaria carica con il più alto impulso trasverso (PT ≳ 1 GeV) in ogni evento. La formazione di un barione eccitato in avanti e il suo decadimento in un barione carico e in raggi γ sono una delle possibili spiegazioni di questo effetto. Si studia anche la correlazione tra il barione eccitato e altre particelle prodotte in ogni interazione.РеэюмеДве змульсионные камеры зкспонировались в протонных пучках 303 ГзВ/с в Ферми Национальной лаборатории ускорителей. Аналиэируется структура 70 событий вэаимодействий протонов с ядрами, сопровождаюшихся гамма-квантами высоких знергий. Наблюдается сиьная корреляция в области фрагментации между гамма-квантами высокой знергии и эаряженной вторичной частицей с больщим поперечным импульсом (Рт≳1 ГзВ/с) в каждом событии. Обраэование воэбужденного бариона и его последуюший распад на эаряженный барион и гамма-кванты является одним иэ воэможных общяснений зтого зффекта. Также исследуется корреляция между воэбужденным барионом и другими обраэованными частицами в каждом вэаимодействии