Review of searches for rare processes and physics beyond the Standard Model at HERA

Abstract

The electron-proton collisions collected by the H1 and ZEUS experiments at HERA comprise a unique particle physics data set, and a comprehensive range of measurements has been performed to provide new insight into the structure of the proton. The high centre of mass energy at HERA has also allowed rare processes to be studied, including the production of W and Z 0 bosons and events with multiple leptons in the final state. The data have also opened up a new domain to searches for physics beyond the Standard Model including contact interactions, leptoquarks, excited fermions and a number of supersymmetric models. This review presents a summary of such results, where the analyses reported correspond to an integrated luminosity of up to 1 fb −1 , representing the complete data set recorded by the H1 and ZEUS experiments.

First QCD analysis of charged hadron fragmentation functions and their uncertainties at next-to-next-to-leading order

“…Parton distribution functions (PDFs) extracted from global QCD fits of deep inelastic electron proton (ep) scattering at HERA as well as proton-(anti)proton (pp) collision at hadron colliders such as LHC, are a fundamental input into hadron collider physics and has been very important in the investigation of the partonic structure of the nucleon, (see [1][2][3][4] for a recent review and [5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21] for recent determination of different types of PDFs). Much effort also have been made by theoretical and experimental particle physics communities to improve our understanding on the partonic structure of the nucleon and nuclei [2,[22][23][24][25][26][27][28][29][30][31][32][33][34][35][36][37][38][39][40][41]. These studies mostly include the the potential of recent measurements at high energy collider to better constrain our present knowledge of the PDFs and the importance or resulting PDFs for predictions of processes at the LHC and possible future high energy and high luminosity lepton and hadron colliders.…”

Signatures of Supersymmetry in Neutrino Telescopes

“…For comparison, we also show the direct limits on |λ 11k | from direct searches in e ± p collisions at HERA with √ s = 319 GeV [124,125], as shown by the magenta-shaded region in Fig. 2 (left).…”

Waiting for the W

“…The only good to come of this is that I realized that the existing calculations at that time had made the same mistake as in the original calculation of p + p → d + W + : they left out the nucleon form factors. The calculations were corrected [Dicus 1986] but the measurement was eventually done at HERA, with e + p → e + W + X [South and Turcato 2016], and also with e + + e + → W + + W − at LEPII [Abdallah 2010]. …”