Johannes Mülmenstädt

Charged particle pseudorapidity density distributions from Au+Au collisions at

The charged-particle pseudorapidity density dN(ch)/d eta has been measured for Au+Au collisions at sqrt[s(NN)] = 130 GeV at RHIC, using the PHOBOS apparatus. The total number of charged particles produced for the 3% most-central Au+Au collisions for /eta/<or=5.4 is found to be 4200+/-470. The evolution of dN(ch)/d eta with centrality is discussed, and compared to model calculations and to data from proton-induced collisions. The data show an enhancement in charged-particle production at midrapidity, while in the fragmentation regions, the results are consistent with expectations from pp and pA scattering.

\sqrt{s_{NN}}

A climatology of thermodynamic phase of precipitating cloud is presented derived from global, land and ocean, retrievals from Cloudsat, CALIPSO, and MODIS. Like precipitation rate, precipitation frequency is dominated by warm rain, defined as rain produced via the liquid phase only, over the tropical oceans outside the ITCZ and by cold rain, produced via the ice phase, over the midlatitude oceans and continents. Warm rain is very infrequent over the continents, with significant warm rain found only in onshore flow in the tropics, and over India, China, and Indochina. Comparison of the properties of precipitating and non-precipitating warm clouds shows that the scarcity of warm rain over land can be explained by smaller effective radii in continental clouds that delay the onset of precipitation. The results highlight the importance of ice-phase processes for the global hydrological cycle and may lead to an improved parameterization of precipitation in general circulation models.

= 130-GeV

Aerosol–cloud–radiation interactions are widely held to be the largest single source of uncertainty in climate model projections of future radiative forcing due to increasing anthropogenic emissions. The underlying causes of this uncertainty among modeled predictions of climate are the gaps in our fundamental understanding of cloud processes. There has been significant progress with both observations and models in addressing these important questions but quantifying them correctly is nontrivial, thus limiting our ability to represent them in global climate models. The Eastern Pacific Emitted Aerosol Cloud Experiment (E-PEACE) 2011 was a targeted aircraft campaign with embedded modeling studies, using the Center for Interdisciplinary Remotely-Piloted Aircraft Studies (CIRPAS) Twin Otter aircraft and the research vessel Point Sur in July and August 2011 off the central coast of California, with a full payload of instruments to measure particle and cloud number, mass, composition, and water uptake distributi...

Frequency of occurrence of rain from liquid-, mixed- and ice-phase clouds derived from A-Train satellite retrievals

Abstract The PHOBOS experiment is well positioned to obtain crucial information about relativistic heavy ion collisions at the Relativistic Heavy Ion Collider (RHIC), combining a multiplicity counter with a multi-particle spectrometer. The multiplicity arrays will measure the charged-particle multiplicity over the full solid angle. The spectrometer will be able to identify particles at mid-rapidity. The experiment is constructed almost exclusively of silicon pad detectors. Detectors of nine different types are configured in the multiplicity and vertex detector (22,000 channels) and two multi-particle spectrometers (120,000 channels). The overall layout of the experiment, testing of the silicon sensors and the performance of the detectors during the engineering run at RHIC in 1999 are discussed.

Eastern Pacific Emitted Aerosol Cloud Experiment

Abstract PHOBOS is one of the four experiments at the Relativistic Heavy Ion Collider at Brookhaven National Laboratory. PHOBOS utilizes silicon sensors to measure charged particle multiplicity distributions and to track particles in a 2-arm spectrometer. The detector consists of 450 silicon pad sensors. Nine different pad geometries are used to match the different physics needs of the experiment. A relatively high granularity, of up to 1536 channels per sensor, is used in the spectrometer. The multiplicity detector uses 128 and 64 channel sensors and the charge deposition per pad is measured to determine the multiplicity of single events. All sensors are of the double-metal silicon pad type with pad sizes from 1 up to 4 cm 2 . They are produced in Taiwan by the ERSO foundry under supervision of Miracle Co. and National Central University. An extensive testing procedure makes it possible to select sensors suited for use in PHOBOS. Detector modules consisting of up to 5 sensors are read out with integrated chips of either 64 or 128 channels. The test results of the sensors and the performance of the assembled detector modules are discussed.

Silicon pad detectors for the PHOBOS experiment at RHIC

AbstractLong time series of Arctic atmospheric measurements are assembled into meteorological categories that can serve as test cases for climate model evaluation. The meteorological categories are established by applying an objective k-means clustering algorithm to 11 years of standard surface-meteorological observations collected from 1 January 2000 to 31 December 2010 at the North Slope of Alaska (NSA) site of the U.S. Department of Energy Atmospheric Radiation Measurement Program (ARM). Four meteorological categories emerge. These meteorological categories constitute the first classification by meteorological regime of a long time series of Arctic meteorological conditions. The synoptic-scale patterns associated with each category, which include well-known synoptic features such as the Aleutian low and Beaufort Sea high, are used to explain the conditions at the NSA site. Cloud properties, which are not used as inputs to the k-means clustering, are found to differ significantly between the regimes and...

The PHOBOS silicon pad sensors

Abstract PHOBOS is one of the four experiments at the Relativistic Heavy Ion Collider at Brookhaven National Laboratory. PHOBOS almost exclusively utilizes silicon sensors to measure charged particle multiplicity distributions and to track particles in a 2-arm spectrometer. The detector consists of about 450 silicon pad sensors. Nine different pad geometries are used to match the different physics needs of the experiment. A relatively high granularity, of up to 1536 channels per sensor, is used in the spectrometer. The multiplicity detector uses 128 and 64 channel sensors and the charge deposition per pad is measured to determine the multiplicity of single events. All sensors are of the double-metal silicon pad type with pad sizes from 1 cm 2 up to 4 cm 2 . They are produced in Taiwan by the ERSO foundry under supervision of Miracle Co. and National Central University. An extensive testing procedure makes it possible to select sensors suited for use in PHOBOS. Detector modules consisting of up to five sensors are read out with integrated chips of either 64 or 128 channels. The testing of the sensors and the performance of assembled detector modules is discussed.

Cloud Properties over the North Slope of Alaska: Identifying the Prevailing Meteorological Regimes

Abstract PHOBOS is one of four experiments at the Relativistic Heavy Ion Collider (RHIC), scheduled to start data collection in fall 1999. Its main goal is to collect events using minimum bias triggers. A search will then be made for interesting, and perhaps rare, classes of events that may indicate the formation of a quark gluon plasma (QGP) or the restoration of chiral symmetry. In this report we describe the PHOBOS detector design and present the first results in detector development. We will also present our expectations from the first year of operation.

The PHOBOS silicon sensors

AbstractIn an influential and interesting study, Stevens (2015) suggested that the global and also Northern Hemispheric warming during the early industrial period implies that the effective radiative forcing by anthropogenic aerosols in the year 2000 compared to 1850 cannot be more negative than −1.0 W m−2. Here results from phase 5 of the Coupled Model Intercomparison Project are analyzed and it is shown that there is little relationship between and the warming trend in the early industrial period in comprehensive climate models. In particular, some models simulate a warming in the early industrial period despite a strong (very negative) . The reason for this difference in results is that the global-mean log-linear scaling of with anthropogenic sulfur dioxide emissions introduced and used by Stevens tends to produce a substantially larger aerosol forcing compared to climate models in the first half of the twentieth century, when SO2 emissions were concentrated over smaller regions. In turn, it shows smal...

The PHOBOS experiment at the RHIC collider

An overview of results for interactions of Au+Au ions at centre-of-mass energies of √sNN = 56, 130 and 200 GeV obtained by the PHOBOS collaboration at RHIC is given. Measurements of primary charged particle density near mid-rapidity indicate that particle production grows logarithmically with collision energy and faster than linearly with the number of interacting nucleons. Elliptic flow is found to be much stronger at RHIC than at SPS energy. The effect is strongest in peripheral events and decreases for more central collisions and emission angles |η| > 1. The measured anti-particle to particle ratios of production rates for pions, kaons and protons in central Au+Au interactions at √sNN = 130 GeV are compatible with the statistical model of particle production, showing an increasingly baryon-free region in mid-rapidity with the increase of collision energy.