6840080
What invariant one-particle multiplicity distributions and two-particle correlations are telling us about relativistic heavy-ion collisions
Many of you are vigorously searching for the quark-gluon plasma—a predicted new phase of nuclear matter where quarks roam almost freely throughout the medium instead of being confined to individual nucleons.1, 2 Such a plasma is believed to have existed in the first 10 μs of the universe during the big bang and could be produced in the laboratory during the little bang of a relativistic heavy-ion collision.
117724729
Particle spectra and interferometry results from NA44
122288526
High pT Physics in the Forward Region
Abstract Two of the most interesting results to emerge from RHIC have been suppression of high p T particles produced at y = 0 in AuAu collisions and a suppression of high p Z particles in d-Au collisions. These have been explained in terms of quark energy loss in the final state and suppression of the initial soft gluon density respectively. In gold-gold collisions one would naively expect the first effect to get weaker and the second stronger with increasing rapidity. Intriguingly the nuclear modification factor shows almost no change with rapdity. We will use several tools to try to understand this result. The theoretical constructs of color glass condensate and quark recombination have been proposed as answers to this problem. The experimental work begins with operational definitions of high p T and forward rapidity and a review of pp collisions. Using a wide range of data on limiting fragmentation, proton/pion ratios and the dependence of R AuAu on energy density we tentatively conclude that the hot partonic matter extends into the forward region and that high p T particles emerge from the surface of this matter.
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.
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.
16904212
Caloric curves and critical behavior in nuclei
Data from a number of different experimental measurements are used to construct caloric curves for five different regions of nuclear mass. These curves are qualitatively similar, and exhibit plateaus at the higher excitation energies. The limiting temperatures represented by the plateaus decrease with increasing nuclear mass, and are in very good agreement with results of recent calculations employing either a chiral symmetry model or the Gogny interaction. This agreement strongly favors a soft equation of state. Evidence is presented which suggests that critical excitation energies and critical temperatures might be determined from caloric curve measurements when the mass variations inherent in such measurements are taken into account.
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.
122525362
DVCS at HERMES: The Recoil Detector & Transverse Target Spin Asymmetries
The HERMES experiment is a large forward angle spectrometer located at the HERA accelerator ring at DESY, Hamburg. One of the most exciting topics studied at HERMES is Deeply Virtual Compton Scattering (DVCS) which is the simplest interaction that provides a gateway for access to Generalised Parton Distributions (GPDs). GPDs are a theoretical framework which can be used to calculate the total angular momentum of the quarks in the nucleon. As such, they provide one piece of the puzzle of nucleonic spin structure. In 2005, HERMES was upgraded in the target region with a Recoil Detector that allows it to make truly exclusive measurements of the DVCS interaction for the first time. The design and construction of the Recoil Detector is discussed herein, in addition to a complete analysis of the Transverse Target Spin Asymmetry (TTSA) in DVCS. Experimental facilities that enable measurement of this asymmetry are rare. The importance of the information on the TTSA from HERMES is made yet greater as the transversely polarised target that allows the asymmetry to be measured has been replaced by an unpolarised target. This was to allow the Recoil Detector to be installed. The final stage of this thesis shows a model-dependent method for constraining the angular momentum of the quarks in the nucleon and speculates as to the other pieces of the spin puzzle.
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.
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.
119217305
Overview of Deeply Virtual Compton Scattering at HERMES
Deeply Virtual Compton Scattering represents the best experimental channel through which to understand Generalised Parton Distributions. The HERMES experiment measured the most diverse set of DVCS results of any experiment; this talk discusses the most recent sets of DVCS results released by HERMES and the unique experimental conditions found at HERMES that facilitated the measurements. We also examine the various ways in which the HERMES experimental measurements are being used to constrain GPDs and how future experiments can learn from the HERMES program.