Quark compositeness, new physics, and ultrahigh-energy cosmic-ray double-core γ-family events

Abstract

We find a significant excess of ultrahigh-energy cosmic-ray events at large transverse moments with respect to the prediction by standard perturbative /CD at E&~b~10 -10 TeV, an energy regime beyond the reach of existing colliders but vnthin the range of future hadron coOiders. Such a large deviation cannot be accounted for by a compositeness model of quarks arith a characteristic energy scale A, & 1.4 TeV allured by current collider experiments, pointing towards neer physics.PACS numbers: 13.85. Tp, 12.38. gk, 12.60.Re, 96.40.De Efforts have been made to search for signals of departures from the standard model in current high-energy studies. For instance, the proliferation of quarks and leptons has naturally inspired the speculation that they are composite bound states of more fundamental constituents called preons [1]. The basic assumption that underlines almost all composite model building is that preons interact by means of a new strong gauge interaction called metacolor. Compositeness of quarks would manifest itself as an effective four-fermion contact interaction which would be visible at momentum transfers well above a characteristic energy scale, A, . Among various ways suggested so far to test the hypothesis, it is particularly interesting to study the behavior of jet inclusive cross sections at large transverse momentum, p2, where effects of a hypothetical quark substructure could result in a deviation from /CD prediction [2]. At existing accelerators, several experiments have been carried out and have yielded null results [3,4]. In the latest experiment at the Fermilab Tevatron pp collider (v/s = 1.8 TeV), no excess of events at large pr with respect to the standard /CD prediction has been observed and the most stringent lower limit of 1.4 TeV has been placed on A, [4].Various limits on the substructure of quarks and leptons have been obtained by studying e+e + e+e, @+is r+r, and qq, KLn, -+ p, e, Kc-K or Ds-D mixing, and the anomalous magnetic moment of muons [1,5].It is of interest to look for such a deviation in jet production cross section in cosmic-ray interactions at even higher energies. We have examined cosmic-ray doublecore events with large p2 observed in emulsion chamber experiments. Extending the leading-order /CD jet calculations for hadron-hadron collisions to hadron-nucleus collisions by including nuclear effects, we have simulated cosmic-ray particle production and propagation in the atmosphere in order to understand quantitatively the double-core events. In this Letter, we report a significant deviation in the jet cross section at large~derived from cosmic-ray data with respect to the calculation by perturbative /CD. Atmospheric cosmic-ray events observed in emulsion chambers installed on mountains at high altitudes provide information about characteristics of the strong interaction at ultrahigh energies. Several such experiments have been carried out for more than a decade, with the goals of searching for new phenomena and studying the mechanism of nuclear collisions in an energy r...

Jet activity versus alignment

“…The detailed studies of double-core (or binocular) phenomena with estimations of event rates and average lateral spread of the γ-family using a PQCD based Monte Carlo can be found, for instance, in [9,10].…”

Are Neutral Goldstone Bosons Initiating Very Energetic Air Showers and Anomalous Multiple-Core Structure as a Component of Cosmic Rays?

“…Recently [6,7,8], these events have been analyzed in terms of high transverse momentum jet production in QCD. The result of this analysis [6,7,8], which must be viewed in the context of limited statistics, is stated to be an order of magnitude excess of events at the largest inferred [8] transverse momenta. It is said to be suggestive of new physics above ∼ 10 16 eV characterized by particle production in the forward direction with unusually large transverse momenta.…”

“…2. Over many years, a number of unusual events of a particular kind [6,7] at high energies have been observed in several photo-emulsion chamber experiments at different high-altitude locations [7]. These events at E lab ∼ 10 16 − 10 17 eV involve double-core γ-families, where a γ-family consists of a bundle of high-energy particles incident on the chamber in almost the same direction.…”

“…In the laboratory, the direction is in the very forward region for the collisions. Recently [6,7,8], these events have been analyzed in terms of high transverse momentum jet production in QCD. The result of this analysis [6,7,8], which must be viewed in the context of limited statistics, is stated to be an order of magnitude excess of events at the largest inferred [8] transverse momenta.…”

“…We show that the possibility for a correlated explanation is provided by new dynamics which arises from collisions of a neutral Goldstone boson as a component of the highest-energy cosmic rays.In this paper, we consider the hypothesis that there is a nearly-massless neutral Goldstone boson, b 0 , which is a component of high-energy cosmic rays and which is initiating air showers [1,2,3] at the highest energies and possibly also anomalous multiple-core structure seen in photo-emulsion chamber experiments [4, 5,6,7,8]. We point out and examine the consequences of new dynamics which arises from the assumption that there is an effective interaction originating in a neutral triangle anomaly [9,10] involving b 0 and a neutral vector boson Z ′ (and/or a chirallyrelated neutral axial vector boson).…”