Large transverse momenta in nuclear interaction at E 0 > 10 16 eV detected in stratosphere
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TESTS OF NEW PHYSICS IN RARE PROCESSES AND COSMIC RAYS (Elementary Particles and Fields: Experiment)
Large Transverse Momenta in Nuclear Interaction at E0 > 1016 eV Detected in Stratosphere* A. K. Managadze1)** , V. I. Osedlo1) , T. M. Roganova1), L. G. Sveshnikova1), V. I. Galkin2) , I. V. Rakobolskaya2), L. A. Goncharova3), K. A. Kotelnikov3), and N. G. Polukhina3) Received November 23, 2005
Abstract—A gamma-hadron superfamily of cosmic-rays created by a primary cosmic-ray particle with energy above 1016 eV was detected at an altitude of 30 km by a stratospheric balloon-borne emulsion chamber. Being of superhigh energy, this event is the unique example in the world statistics of practically pure nuclear interactions in the energy range unattainable for modern accelerators. The present analysis allowed one to estimate the interaction height above the chamber and transverse momenta of the secondaries produced in the interaction. The mean value of transverse momenta appears to be very large (pt > 2.5 GeV/c). PACS numbers : 96.40.Cd DOI: 10.1134/S1063778807010231
1. INTRODUCTION In 1975, the unique gamma-hadron family with energy above 1016 eV was detected by a balloonborne emulsion chamber at 30-km altitude in the stratosphere [1]. This event named STRANA is supposed to be the result of a single nuclear interaction undistorted by cascade degradation due to the very thin air layer above the chamber (about 10 g/cm2 ). Now the superfamily has been reanalyzed, using modern model simulations and a new measuring technique. By reconsidering the event, clear evidence of an alignment effect (arrangement of particle tracks along a straight line in a film resulting from coplanar scattering of secondaries in the interaction) was found [2, 3]. It is consistent with the facts of alignment observed in the same energy range >1016 eV in mountain emulsion experiments [4, 5]. For evident display of alignment, the necessity of a large-transverse-momentum phenomenon was presumed [6, 7]. In contrast to mountain experiments, a stratospheric event does not exclude the possibility to estimate interaction height above the installation and consequently to determine transverse momenta ∗
The text was submitted by the authors in English. Institute of Nuclear Physics, Moscow State University, Moscow, 119992 Russia. 2) Faculty of Physics, Moscow State University, Moscow, 119992 Russia. 3) Lebedev Institute of Physics, Russian Academy of Sciences, Leninskiy pr. 53, Moscow, 117924 Russia. ** E-mail: [email protected] 1)
in the interaction. The STRANA superfamily is the only event in the world statistics having such high energy and being the result of a “pure” nuclear interaction. Therefore, the determination of pt in such an event is a rather important aim. 2. EXPERIMENT The flight was carried out from the Kamchatka peninsula to the Volga River for 160 h, the detection probability for an event with such high energy was less than 10−4 . The emulsion chamber (Fig. 1) with area 40 × 50 cm2 consisted of three blocks: a target, a spacer, and a lead
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