Measurement of Anti-Deuteron Photoproduction and a Search for Heavy Stable Charged Particles at HERA

TL;DR

This paper measures the production rate of anti-deuterons in photon-proton collisions at HERA and searches for heavy stable charged particles, providing insights into anti-matter formation and particle production mechanisms.

Contribution

It presents the first measurement of anti-deuteron photoproduction cross sections and the coalescence parameter B_2 at HERA, and sets upper limits on heavy stable charged particle production.

Findings

Anti-deuteron production rate similar to proton-proton collisions at CERN ISR.

Coalescence parameter B_2 measured to be 0.010, higher than in Au-Au collisions.

No significant production of heavier particles observed, upper limits set.

Abstract

The cross section for anti-deuteron photoproduction is measured at HERA at a mean centre-of-mass energy of W_{\gamma p} = 200 GeV in the range 0.2 < p_T/M < 0.7 and |y| < 0.4, where M, p_T and y are the mass, transverse momentum and rapidity in the laboratory frame of the anti-deuteron, respectively. The numbers of anti-deuterons per event are found to be similar in photoproduction to those in central proton-proton collisions at the CERN ISR but much lower than those in central Au-Au collisions at RHIC. The coalescence parameter B_2, which characterizes the likelihood of anti-deuteron production, is measured in photoproduction to be 0.010 \pm 0.002 \pm 0.001, which is much higher than in Au-Au collisions at a similar nucleon-nucleon centre-of-mass energy. No significant production of particles heavier than deuterons is observed and upper limits are set on the photoproduction cross sections for such particles.