Measuring Photons and Neutrons at Zero Degrees in CMS

Abstract

The CMS Zero Degree Calorimeters, ZDCs, will measure photons and neutrons emitted with |η| ≥ 8.6 from Pb+Pb, p+Pb and p+p collisions at √ s N N = 5.5, 8.8 and 14 TeV respectively. The calorimeter consists of an electromagnetic part segmented in the horizontal direction and an hadronic part segmented into four units in depth. In addition CMS will have access to data from a segmented shower maximum detector being built for luminosity measurements. We will present detailed results from tests beam measurements taken at the CERN SPS. These data will be used to extrapolate the utility of the ZDCs to measure photons, and possibly π 0 s in p+p and ultra-peripheral heavy-ion collisions. Data from the hadronic section can be used to estimate the number of participants in heavy ion-collisions. In addition we will discuss plans to use the detector to measure the reaction plane, thereby extending the sensitivity of the central detectors in CMS.

The Development of the CMS Zero Degree Calorimeters to Derive the Centrality of AA Collisions

“…The ZDC signals from pure electromagnetic events were found to be Gaussian distri- butions, and the signals from hadronic events were found to be Landau distributions [52,53]. An example of a pure electromagnetic response is given in…”

Study of Very Forward Neutrons with the CMS Zero Degree Calorimeter

“…This paper presents results using the EM and HAD sections of the ZDC detector on the lead going side (z < 0) measured in pPb collisions at the CMS experiment in 2016. A more detailed description of the ZDC detectors can be found in references [17][18][19][20]. Every channel of the detector is read out in 10 timeslices (denoted with TS0 -TS9), each 25 ns long.…”

Performance of the CMS Zero Degree Calorimeters in the 2016 pPb run

“…They reside in special detector slots in the neutral particle absorber (TAN), which protects the first superconducting quadrupole magnet from radiation. A full description of the ZDC can be found in [3][4][5][6]. Located inside the TAN at pseudorapidity η greater than 8.3 corresponding roughly to θ < 0.5 mrad, the ZDCs detect photons and those neutral particles that are not swept away by bending and focusing magnets between the interaction point and the ZDCs.…”