Precision for LHC from combined HERA data

H1 collaboration

ZEUS collaboration

The H1 and ZEUS collaborations have submitted three common publications opening a new era of precision in the analysis of electron-proton data collected at the high energy collider HERA at DESY. HERA was capable to collide both electrons and their anti-particles, positrons on protons, thereby providing a unique experimental configuration. The publications contain the result from an analysis performed by both experiments using the HERA collider data, which consists of up to 2 billion electron-proton interactions recorded over a period of 15 years between 1992 and 2007. The first of the publications, signed by 550 authors from 91 institutes and 30 countries, has now been accepted for publication by the peer reviewed Journal for High energy Physics (JHEP).

By combining their data the experiments achieve a significant increase in the sensitivity to the proton structure. The combination of the two data sets minimizes the systematic errors in the measurements, leading to a large improvement over individual experiments. The published data are of particular importance for the Large Hadron Collider, which will start soon colliding protons at CERN. The unique domain accessed by HERA experiments in this joint analysis and the tantalizing experimental precision obtained via refined experimental techniques will lead to an improved understanding of the fundamental structure of matter. This will consolidate the research for new phenomena at LHC.

The other two publications contain analyses of the events with energetic leptons in configurations that are only rarely produced in electron-proton collisions, according to the current theory of particle interactions, also known as the Standard Model. The studies, based on the full data set, observe a few spectacular events, the rate of which exceeds, but is still statistically compatible with the Standard Model prediction.

Further similar results of the HERA collaborations are expected in the next years using the full data sets of the collider experiments.

Luigi Rolandi from CERN, member of the JHEP editorial board, commented: "These joint papers are a nice example of how science progresses with mutual constructive interaction: putting together the whole available information one gets a more precise conclusion. The important point is indeed the increase of precision of the experimental measurement. I am especially happy that the two Collaborations decided to submit these important papers to JHEP supporting its Open Access philosophy."

More information on the combined data and the submitted papers are available here.