Acceptance Corrections and Extreme-Independent Models in Relativistic Heavy Ion Collisions

Kopeliovich's suggestion [nucl-th/0306044] to perform nuclear geometry (Glauber) calculations using different cross sections according to the experimental configuration is quite different from the standard practice of the last 20 years and leads to a different nuclear geometry definition for each experiment. The standard procedure for experimentalists is to perform the nuclear geometry calculation using the total inelastic N-N cross section, which results in a common nuclear geometry definition for all experiments. The incomplete acceptance of individual experiments is taken into account by correcting the detector response for the probability of measuring zero for an inelastic collision, which can often be determined experimentally. This clearly separates experimental issues such as different acceptances from theoretical issues which should apply in general to all experiments. Extreme-Independent models are used to illustrate the conditions for which the two methods give consistent or inconsistent results.Comment: 4 pages, 1 figure, published in Physical Review

Simultaneous measurement of spatially resolved particle emissions in a pilot plant scale baghouse filter applying distributed low-cost particulate matter sensors

Baghouse filters are widely applied in industrial gas cleaning, for example in waste incineration plants and the cement industry, to meet particle emission standards and for product recovery. The global particle emission of pulse-jet cleaned surface filters is typically monitored end of pipe (e.g. in the stack). Since the particulate matter emission of baghouse filters originates often from leaks and incorrectly installed or damaged filter bags, operators would greatly profit from online measurement technology that monitors the emission contribution of individual filter bags or at least a subset of all installed filter elements to the total emission. Low-cost particulate matter sensors can be deployed inside filter houses in larger quantities due to their compact design and low asset cost compared to conventional aerosol measurement technology. The ability of several low-cost sensors to detect the characteristic PM emission behavior of surface filters has been shown in previous investigations in a filter test rig. This study shows first results regarding the emission contribution of individual filter bags of a pilot plant scale baghouse filter employing distributed low-cost sensors of the model OPC-N3 from the manufacturer Alphasense. A Promo® 2000 aerosol spectrometer with a welas® 2100 sensor serves as reference regarding the particulate matter concentration detected by the low-cost sensors and as end of pipe measurement equipment to monitor the global emission. The selected filter medium was a membrane filter medium with sealed seams to provide low emission levels and defined conditions on the clean gas side. The employed low-cost sensors detect an emission peak right after cleaning of the corresponding filter bag only. The global emission measured in the clean gas duct consists of the overlay of the individual emission peaks detected locally at the corresponding filter bags. By exchanging one filter bag with a filter bag made from a non-membrane filter medium without sealed seams, an increase of the total continuous emission can be detected, both end of pipe in the clean gas duct and locally via the low-cost particulate matter sensor. This demonstrates the applicability of the measurement technology for the detection and identification of leaks and damaged filter bags that serve as emission hotspots in baghouse filters

Impact of ambient air filters on PM concentration levels at an urban traffic hotspot (Stuttgart, Am Neckartor)

Air pollution can have severe impacts on public health. A novel approach to lower the local particle concentrations at urban hotspots is ambient air filtration. This study presents experimental investigations into the effectiveness of air filters to lower ambient particle concentration levels at two different locations. Seventeen outdoor filtration devices with a total flow rate of 170.000 m³/h were installed beside federal highway B14 at Stuttgart “Am Neckartor” targeting to reduce PM10 concentration levels within a 300 m × 50 m area around the urban pollution hotspot. Further measurements were conducted at the residential area “Bleyle quarter” to show the capabilities of a single filter device under relatively defined conditions. By periodically switching the filters on and off while monitoring the particle mass concentrations with optical particle counters, the effects of the filters on the PM10 and PM2.5 concentration levels were determined. A long term investigation at the Neckartor installation site (466 h) yielded an average PM10 reduction of 10.4% (6.3 μg/m³) at the official Neckartor measurement station. Additional in situ measurement campaigns showed that the PM reduction effect decreases with increasing distance to the filter devices. However, the effect is clearly measurable in the walkway areas across the installation site

Proton stopping in C+C, d+C, C+Ta and d+Ta collisions at 4.2A GeV/c

The shape of proton rapidity distributions is analysed in terms of their Gaussian components, and the average rapidity loss is determined in order to estimate the amount of stopping in C+C, d+C, C+Ta and d+Ta collisions at 4.2A GeV/c. Three Gaussians correspond to the nuclear transparency and describe well all peripheral and also C+C central collisions. Two-component shape is obtained in case of d+C and C+Ta central collisions. Finally one Gaussian, found in d+Ta central collisions, corresponds to the full stopping. The calculated values of the average rapidity loss support the qualitative relationship between the number of Gaussian components and the corresponding stopping power. It is also observed, in central collisions, that the average rapidity loss increases with the ratio of the number of target and the number of projectile participants.Comment: 9 pages REVTeX, 1 PS figure replaced, to be published in Phys.Rev.

Intermittency and Exotic Channels

It is pointed out that accurate measurements of short-range two-particle correlations in like-charge $K\pi$ and in $\pi^ 0\pi^ 0$ channels should be very helpful in determining the origin of the \lq\lq intermittency\rq\rq\ phenomenon observed recently for the like-charge pion pairs.Comment: 5 p., plain tex, preprint T94/078(Saclay), LPTHE 94/58(Orsay

Thermal analysis of hadron multiplicities from relativistic quantum molecular dynamics

Some questions arising in the application of the thermal model to hadron production in heavy ion collisions are studied. We do so by applying the thermal model of hadron production to particle yields calculated by the microscopic transport model RQMD(v2.3). We study the bias of incomplete information about the final hadronic state on the extraction of thermal parameters.It is found that the subset of particles measured typically in the experiments looks more thermal than the complete set of stable particles. The hadrons which show the largest deviations from thermal behaviour in RQMD(v2.3) are the multistrange baryons and antibaryons. We also looked at the influence of rapidity cuts on the extraction of thermal parameters and found that they lead to different thermal parameters and larger disagreement between the RQMD yields and the thermal model.Comment: 12 pages, 2 figures, uses REVTEX, only misprint and stylistic corrections, to appear in Physical Review

Freeze-Out Time in Ultrarelativistic Heavy Ion Collisions from Coulomb Effects in Transverse Pion Spectra

The influence of the nuclear Coulomb field on transverse spectra of $\pi^+$ and $\pi^-$ measured in $Pb+Pb$ reactions at 158 A GeV has been investigated. Pion trajectories are calculated in the field of an expanding fireball. The observed enhancement of the $\pi^-/\pi^+$ ratio at small momenta depends on the temperature and transverse expansion velocity of the source, the rapidity distribution of the net positive charge, and mainly the time of the freeze-out.Comment: 11 pages including 2 figure

Relativistic Heavy--Ion Collisions in the Dynamical String--Parton Model

We develop and extend the dynamical string parton model. This model, which is based on the salient features of QCD, uses classical Nambu-Got\=o strings with the endpoints identified as partons, an invariant string breaking model of the hadronization process, and interactions described as quark-quark interactions. In this work, the original model is extended to include a phenomenological quantization of the mass of the strings, an analytical technique for treating the incident nucleons as a distribution of string configurations determined by the experimentally measured structure function, the inclusion of the gluonic content of the nucleon through the introduction of purely gluonic strings, and the use of a hard parton-parton interaction taken from perturbative QCD combined with a phenomenological soft interaction. The limited number of parameters in the model are adjusted to $e^+e^-$ and $p$--$p$ data. Utilizing these parameters, the first calculations of the model for $p$--$A$ and $A$--$A$ collisions are presented and found to be in reasonable agreement with a broad set of data.Comment: 26 pages of text with 23 Postscript figures placed in tex

Mapping out the QCD phase transition in multiparticle production

We analyze multiparticle production in a thermal framework for 7 central nucleus nucleus collisions, $e^+$+ $e^-$ annihilation into hadrons on the Z resonance and 4 hadronic reactions (p+p and p+$\bar{p}$ with partial centrality selec tion), with center of mass energies ranging from $\sqrt{s}$= 2.6 GeV (per nucleon pair) to 1.8 TeV. Thermodynamic parameters at chemical freeze-out (temperature and baryon and strangeness fugacities) are obtained from appropriate fits, generally improving in quality for reactions subjected to centrality cuts. All systems with nonvanishing fugacities are extrapolated along trajectories of equal energy density, density and entropy density to zero fugacities. The so obtained temperatures extrapolated to zero fugacities as a function of initial energy density $\epsilon_{in}$ universally show a strong rise followed by a saturating limit of $T_{lim}$ = 155 $\pm$ 6 $\pm$ 20 MeV. We interpret this behaviour as mapping out the boundary between quark gluon plasma and hadronic phases. The ratio of strange antiquarks to light ones as a function of the initial energy density $\epsilon_{in}$ shows the same behaviour as the temperature, saturating at a value of 0.365 $\pm$ 0.033 $\pm$ 0.07. No distinctive feature of 'strangeness enhancement' is seen for heavy ion collisions relative to hadronic and leptonic reactions, when compared at the same initial energy density