Multiplicity Studies and Effective Energy in ALICE at the LHC

In this work we explore the possibility to perform ``effective energy'' studies in very high energy collisions at the CERN Large Hadron Collider (LHC). In particular, we focus on the possibility to measure in $pp$ collisions the average charged multiplicity as a function of the effective energy with the ALICE experiment, using its capability to measure the energy of the leading baryons with the Zero Degree Calorimeters. Analyses of this kind have been done at lower centre--of--mass energies and have shown that, once the appropriate kinematic variables are chosen, particle production is characterized by universal properties: no matter the nature of the interacting particles, the final states have identical features. Assuming that this universality picture can be extended to {\it ion--ion} collisions, as suggested by recent results from RHIC experiments, a novel approach based on the scaling hypothesis for limiting fragmentation has been used to derive the expected charged event multiplicity in $AA$ interactions at LHC. This leads to scenarios where the multiplicity is significantly lower compared to most of the predictions from the models currently used to describe high energy $AA$ collisions. A mean charged multiplicity of about 1000-2000 per rapidity unit (at $\eta \sim 0$) is expected for the most central $Pb-Pb$ collisions at $\sqrt{s_{NN}} = 5.5 TeV$.Comment: 12 pages, 19 figures. In memory of A. Smirnitski

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Structural Assembly from Phosphate to Germanophosphate by Applying Germanate as a Binder

National Natural Science Foundation of China [21201144, 21233004, 40972035]; Fundamental Research Funds for the Central Universities [2013121020]; Technological Innovation Platform of Fujian Province [2006L2003]Structural assembly from phosphate to germanophosphate by applying germanate as a binder has been achieved. Two isotypic porous compounds, K-3 [M-4(II)(HPO4)(2)][Ge2O(OH)(PO4)(4)]center dot xH(2)O (M-II = Fe, Cd; x = 2 for Fe and 3 for Cd, denoted as KFeGePO-1 and KCdGePO-1, respectively), contain a known transition-metal phosphate (TMPO) layer, (2)(infinity){[M-2(HPO4)(3)](2-)}, which is built from chains of trans-edge-sharing MO6 octahedra bridged by MO5 trigonal bipyramids that were further linked and decorated by phosphate tetrahedra. The layers are bound by infinite chains of GeO5(OH) octahedra, resulting in a 3D open-framework structure with 1D 12-ring channels that are occupied by K+ ions and water molecules. The curvature of the TMPO layers and shape of the 12-ring windows can be tuned by the transition metals because of their Jahn-Teller effect

Final test of the MRPC production for the ALICE TOF detector

During the autumn of 2006 a final test of a sample of double-stack MRPC (Multigap Resistive Plate Chamber) strips, randomly chosen from two years of mass production (the ALICE Time-Of-Flight detector is made of 1638 strips), was carried out at the CERN Proton Synchrotron facility. The results on the performances of the MRPCs and of the front-end and readout electronics will be presented. it is confirmed that these devices have a very good uniformity of response, a long streamer-free plateau, an efficiency higher than 99% and an "intrinsic" time resolution better than about 40 ps

Tools to monitor the quality of the ALICE-TOF detector data.

Since the beginning of commissioning of the ALICE-TOF detector, one of the most crucial aspects has been to check the quality of the data produced. Both during last November tests at the CERN PS and in the cosmic-ray test facility, running since more than one year, the data taking of assembled TOF modules has been continuously monitored in order to detect as quickly as possible faulty conditions or bad detector configurations. The tools developed for these purposes, which are currently also used for the commissioning of TOF SuperModules, and the new under-development automatic data quality monitor will ensure the highest possible TOF data quality during its operation

First commissioning results of ALICE-TOF SuperModules.

This paper describes the main quality assurance tests developed to check the status of the ALICE TOF SuperModules and included in the commissioning procedures. Some preliminary results concerning these tests on the first two installed super modules are presented as well

Space charge limited avalanche growth in multigap resistive plate chambers

The ALICE TOF array will be built using the Multigap Resistive Plate Chamber(MRPC) configured as a double stack. Each stack contains 5 gas gaps with width of 250 μm. There has been an intense R&D effort to optimise this new detector to withstand the problems connected with the high level of radiation at the LHC. One clear outcome of the R&D is that the growth of the gas avalanche is strongly affected by space charge. The effect of the space charge is a decrease in the rate of change in gain with electric field; this allows more stable operation of this detector. We have measured the gain as a function of the electric field and also measured the ratio of the fast charge to the total charge produced in the gas gap. It is well established that RPCs built with 250 μm gas gap have a much superior performance than 2 mm gaps; we discuss and compare the performance of 250 μm gap MRPCs with 2 mm gap RPCs to show the importance of space-charge limitation of avalanche growth. PACS: 29.40.Cs – 7.77.-n – 52.80.D

Quality assurance procedures for the construction of ALICE TOF SuperModules

This paper describes the set of quality assurance procedures developed to check the status of the ALICE TOF Super Modules. Some preliminary results are presented as well

Design aspects and prototype test of a very precise TDC system implemented for the multigap RPC of the ALICE-TOF

The ALICE Time-of-Flight system will be a large area (150m**2) detector made by Multigap RPC (MRPC). T he time digitisation is based on the High Performance TDC chip (HPTDC). Tests carried out on board prototypes are discussed, emphasising the optimisation of the effective time resolution of the chip when working in its Very High Resolution Mode. Lab bench tests and test beam results show that a 20 ps resolution has been achieved