118432204
Particle spectra and HBT results from NA44
Recent results on baryon spectra and interferometry from NA44 are compared to RQMD and a hydrodynamical model. The importance of flow and rescattering on the rapidity and transverse mass distributions is discussed. The yields of protons and antiprotons are compared as a function of system, rapidity and multiplicity.
118954806
Measuring photons and neutrons at zero degrees in CMS
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 , 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 π0s 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.
119206647
Commissioning of CMS zero degree calorimeter using LHC beam
This paper reports on the commissioning and first running experience of the CMS Zero Degree Calorimeters during December 2009. All channels worked correctly. The ZDCs were timed into the data acquisition system using beam splash events. These data also allowed us to make a first estimate of channel-by-channel variations in gain.
122020676
Heavy Ions with CMS: The Central Region
The potential of CMS as a heavy ion detector is described with special emphasis on the study of the central rapidity region. The detector provides excellent measurements of leptons, photons, gauge bosons, jets and quarkonia. Thus CMS serves as an unbiased detector for Pb+Pb events at \(\sqrt {S_{nn} } = 5.5\) TeV.
119510186
Anti)proton and pion source sizes and phase space densities in heavy ion collisions
NA44 has measured midrapidity deuteron spectra from $\mathrm{AA}$ collisions at $\sqrt{{s}_{\mathrm{nn}}}\ensuremath{\approx}18$ GeV at the CERN SPS. Combining these spectra with published p, $\overline{p},$ and $\overline{d}$ data allows us to calculate, within a coalescence framework, p and $\overline{p}$ source sizes and phase space densities. These results are compared to ${\ensuremath{\pi}}^{\ifmmode\pm\else\textpm\fi{}}$ source sizes measured by Hanbury Brown\char21{}Twiss (HBT) interferometry and phase densities produced by combining pion spectra and HBT results. We also compare to $\mathrm{pA}$ results and to lower energy (AGS) data. The $\overline{p}$ source is larger than the proton source at $\sqrt{{s}_{\mathrm{nn}}}=17.3$ GeV. The phase space densities of ${\ensuremath{\pi}}^{+}$ and p are not constant but grow with system size. Both ${\ensuremath{\pi}}^{+}$ and proton radii decrease with ${m}_{T}$ and increase with $\sqrt{{s}_{\mathrm{nn}}}.$ Pions and protons do not freeze out independently. The nature of their interaction changes as $\sqrt{{s}_{\mathrm{nn}}}$ and the $\ensuremath{\pi}/p$ ratio increases.
121158428
Search for Hawking radiation in heavy ion collisions
The creation of “white holes” that decay by Hawking radiation has been proposed as one way to achieve the very early thermalization observed in heavy ion collisions at RHIC. The charartistic temperature of the radiations depends only on the ratio of the baryon number to the transverse energy. The yields of pions, kaons, protons and antiprotons measured by BRAHMS in central Au+Au collisions can be described within a thermal model where T drops with rapidity, and beam energy. We find that the chemical freeze-out temperature drops as the ratio of baryon number to energy increases but much more rapidly than predicted by the model.
120848137
The bar PANDA focussing-lightguide disc DIRC
ANDA will be a fixed target experiment internal to the HESR antiproton storage ring at the future FAIR complex. The ANDA detector requires excellent particle-identification capabilities in order to achieve its scientific potential. Cherenkov counters employing the DIRC principle were chosen as PID detectors for the Target Spectrometer. The proposed Focussing-Lightguide Disc DIRC will cover the forward part of the Target Spectrometer acceptance in the angular range between 5° and 22°. Its design includes a novel approach to mitigate dispersion effects in the solid radiator of a DIRC counter using optical elements. The dispersion correction will enable the Focussing-Lightguide Disc DIRC to provide pion-kaon identification for momenta well above 3.5 GeV/c.
120484753
The front-end readout electronics for the P̄ANDA Focussing-Lightguide Disc DIRC
One of the key detectors of the upcoming ANDA experiment for particle identification will be the Focussing-Lightguide Disc DIRC, based on a novel detector technique. It will use a fused silica disc as a solid radiator to generate Cherenkov light by the passing of charged particles. These photons will be transported by total-internal-reflection to the rim, where LiF crystals will be used to perform dispersion corrections. Focussing lightguides will map propagation angles to spatial positions on the surface of photon detectors. Fast single photon detection devices will be used to measure azimuthal angles and spatial positions, which can be used to reconstruct kinematic properties of the passing particles. The expected average interaction rate of 20 MHz yields a photon detection rate of 1.3 MHz, as it is foreseen to use 128 MCP-PMT, each with 32 channels, for continuous readout. Moderate timing resolution of 300 ps improves signal from noise separation. The readout design requirements for the Focussing-Lightguide Disc DIRC will be introduced. The current candidate for implementation of the front-end readout electronic system will be described and several alternative readout scenarios will be discussed. Finally, a summary and an outlook for further developments and tests will be given.
119536751
The Focusing Disc DIRC for the PANDA experiment at FAIR
The Focusing Disc DIRC is a novel detector concept for particle identification based on the detection of internally-reflected Cherenkov light. A thin synthetic silica disc of 1 m radius will be used as radiator and for light transportation. At the rim LiF bars are foreseen to passively correct for dispersion. Focusing elements map the angles of the propagating photons to spatial positions on the focal plane covered with position sensitive photon detection devices. This novel 2D(+1t) detector concept will contribute to the outstanding particle identification performance of the general purpose PANDA detector. The aims of the PANDA experiment are to address fundamental questions of the strong force, to explore the structure of the nucleon and to search for new matter. The technical design, the current status of the development and recent results from prototype test experiments for the Focusing Disc DIRC are presented.
123332232
Hard exclusive measurements with a polarised target at HERMES
Hard exclusive measurements at HERMES provide access to the information framework of Generalised Parton Distributions. This framework has the potential to provide a thorough, phenomenological description of the nucleon and aspects of it can be constrained by recent measurements made at the HERMES experiment at DESY. Consideration of meson production allows access to some GPDs, whilst observables from the deeply virtual Compton scattering process can allow a constraint on model parameters which are directly connected to the total angular momentum contribution of up and down quarks to the nucleon's spin.