Prospects for the detection of the chargino-neutralino direct production with the ATLAS detector at the LHC

The Large Hadron Collider (LHC), currently under installation at CERN, is designed to provide high-energy proton collisions at the TeV energy scale, with a large instantaneous luminosity. This will allow to explore an energy region never reached by the previous accelerators and to search for new physics, also beyond the Standard Model (SM), as expected by a wide range of models. ATLAS (A Toroidal LHC Apparatus) is one of the four experiments which will be installed at the LHC. It is a general-purpose experiment which address the investigation of the full discovery potential provided by the LHC. Chapter 1 is dedicated to the description of the accelerator, the ATLAS experiment and its discovery capabilities. ATLAS is a large and complex experiment, accounting roughly $10^8$ electronic channels. Its trigger and data acquisition systems will be able to select and save few interesting events in between millions. Hence, to bring ATLAS to its maximum performances, a complete and effective monitoring system, able to facilitate the reaching of the correct running conditions and the assessing of the data quality, will be needed. The development of such monitoring tools started during the past beam tests and, at present, it continues supporting the detector commissioning and installation phase. In chapter 2, the development of a lightweight low-level monitoring framework, devoted to the hardware-functionality monitoring, is discussed. Presently the SM is not considered as an ultimate theory, and therefore new models are studied in order to find answers to open questions. Among these theories, the supersymmetries provide a framework that can possibly solve some theoretical problems, such as the hierarchy problem. Up to now, no experimental evidences of supersymmetries were found, however, if they exist, the LHC experiments could possibly find their signatures. An introduction to supersymmetrical theories, particularly focused on gaugino physics, is the object of chapter 3. Among the several signatures predicted by the supersymmetric models, the decay of $\tilde\chi_0^2\tilde\chi_1^\pm$ gaugino pairs into three leptons and missing transverse energy is particularly interesting. Indeed this channel has a low SM backgrounds, especially from QCD, and can provide information on the model parameters. Hence, we developed, through fast simulation data, a search strategy for the trilepton channel, within the ATLAS detector, for a large number of models. The results of this analysis are reported in chapter 4. Most of the LHC discovery potential is driven by its large target luminosity of $10^{34}$ cm$^{-2}$s$^{-1}$. However, to reach this target, fine optimizations of beam optics and tuning are necessary. Moreover, experiments may need to know the bunch-by-bunch luminosity, in order to correct physics results for pile-up events. Hence, a luminometer, able to high-precision bunch-by-bunch relative luminosity measurements, will be an effective tool both for the accelerator and the experiments. In chapter 5, the development of a LHC luminometer, based on a fast radiation-hard argon ionization chamber, performed at the Lawrence Berkeley National Laboratory, is discussed

GNAM and OHP: Monitoring Tools for ATLAS experiment at LHC.

ATLAS is one of the four experiments under construction along the Large Hadron Collider (LHC) ring at CERN. The LHC will produce interactions at a center-of-mass energy equal to âs = 14 TeV at 40 MHz rate. The detector consists of more than 140 million electronic channels. The challenging experimental environment and the extreme detector complexity impose the necessity of a common scalable distributed monitoring framework, which can be tuned for the optimal use by different ATLAS sub-detectors at the various levels of the ATLAS data flow. This note presents two monitoring tools that have been developed for this aim within the architecture ATLAS Monitoring Framework and the Data Acquisition System: GNAM and OHP. The first one is a framework for online histogram production; the second one is graphical application for histogram presentation. This tools are now widely used during the ATLAS commissioning and their performances are reported in this not

The ROD crate DAQ software framework of the ATLAS data acquisition system

In the ATLAS experiment at the LHC, the ROD Crate DAQ provides a complete software framework to implement data acquisition functionality at the boundary between the detector specific electronics and the common part of the data acquisition system. Based on a plugin mechanism, it allows selecting and using common services (like data output and data monitoring channels) and developing software to control and acquire data from detector specific modules providing the infrastructure for control, monitoring and calibration. Including also event building functionality, the ROD Crate DAQ is intended to be the main data acquisition tool for the first phase of detector commissioning. This paper presents the design, functionality and performance of the ROD Crate DAQ and its usage in the ATLAS data acquisition system and during detector tests

The ATLAS MDT remote calibration centers

The precision chambers of the ATLAS Muon Spectrometer are built with Monitored Drift Tubes (MDT). The requirement of high accuracy and low systematic error, to achieve a transverse momentum resolution of 10% at 1 TeV, can only be accomplished if the calibrations are known with an accuracy of 20 μm. The relation between the drift path and the measured time (the socalled r-t relation) depends on many parameters (temperature T, hit rate, gas composition, thresholds,...) subject to time variations. The r-t relation has to be measured from the data without the use of an external detector, using the autocalibration technique. This method relies on an iterative procedure applied to the same data sample, starting from a preliminary set of constants. The required precision can be achieved using a large (few thousand) number of non-parallel tracks crossing a region, called calibration region, i.e. the region of the MDT chamber sharing the same r-t relation.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/85421/1/jpconf10_219_022028.pd

The ATLAS Readout System for LHC Runs 2 and 3

The ReadOut System (ROS) is a central part of the data acquisition (DAQ) system of the ATLAS Experiment at the CERN Large Hadron Collider (LHC). The system is responsible for receiving and buffering event data from all detector subsystems and serving these to the High Level Trigger (HLT) system via a 10 GbE network, discarding or transporting data onward once the trigger has completed its selection process. The ATLAS ROS was completely replaced during the 2013-2014 experimental shutdown in order to meet the demanding conditions expected during LHC Run 2 and Run 3 (2015-2025). The ROS consists of roughly one hundred Linux-based 2U-high rack-mounted servers equipped with PCIe I/O cards and 10 GbE interfaces. This paper documents the system requirements for LHC Runs 2 and 3 and the design choices taken to meet them. The results of performance measurements and the re-use of ROS technology for the development of data sources, test platforms for other systems, and another ATLAS DAQ system component, namely the Region of Interest Builder (RoIB), are also discussed. Finally performance results for Run 2 operations are presented before looking at the upgrade for Run 3.Comment: 40 pages, 18 figures, journal pape

Scintillation particle detection based on microfluidics

A novel type of particle detector based on scintillation, with precise spatial resolution and high radiation hardness, is being studied. It consists of a single microfluidic channel filled with a liquid scintillator and is designed to define an array of scintillating waveguides each independently coupled to a photodetector. Prototype detectors built using an SU-8 epoxy resin have been tested with electrons from a radioactive source. The experimental results show a light yield compatible with the theoretical expectations and confirm the validity of the approach

Dual-Readout Calorimetry with Lead Tungstate Crystals

Results are presented of beam tests in which a small electromagnetic calorimeter consisting of lead tungstate crystals was exposed to 50 GeV electrons and pions. This calorimeter was backed up by the DREAM Dual-Readout calorimeter, which measures the scintillation and \v{C}erenkov light produced in the shower development, using two different media. The signals from the crystal calorimeter were analyzed in great detail in an attempt to determine the contributions from these two types of light to the signals, event by event. This information makes it possible to eliminate the dominating source of fluctuations and thus achieve an important improvement in hadronic calorimeter performance.Comment: Preprint submitted to Nucl. Instrum. Meth. on July 23, 200

System Test of the ATLAS Muon Spectrometer in the H8 Beam at the CERN SPS

An extensive system test of the ATLAS muon spectrometer has been performed in the H8 beam line at the CERN SPS during the last four years. This spectrometer will use pressurized Monitored Drift Tube (MDT) chambers and Cathode Strip Chambers (CSC) for precision tracking, Resistive Plate Chambers (RPCs) for triggering in the barrel and Thin Gap Chambers (TGCs) for triggering in the end-cap region. The test set-up emulates one projective tower of the barrel (six MDT chambers and six RPCs) and one end-cap octant (six MDT chambers, A CSC and three TGCs). The barrel and end-cap stands have also been equipped with optical alignment systems, aiming at a relative positioning of the precision chambers in each tower to 30-40 micrometers. In addition to the performance of the detectors and the alignment scheme, many other systems aspects of the ATLAS muon spectrometer have been tested and validated with this setup, such as the mechanical detector integration and installation, the detector control system, the data acquisition, high level trigger software and off-line event reconstruction. Measurements with muon energies ranging from 20 to 300 GeV have allowed measuring the trigger and tracking performance of this set-up, in a configuration very similar to the final spectrometer. A special bunched muon beam with 25 ns bunch spacing, emulating the LHC bunch structure, has been used to study the timing resolution and bunch identification performance of the trigger chambers. The ATLAS first-level trigger chain has been operated with muon trigger signals for the first time

Evidence for the h_b(1P) meson in the decay Upsilon(3S) --> pi0 h_b(1P)

Using a sample of 122 million Upsilon(3S) events recorded with the BaBar detector at the PEP-II asymmetric-energy e+e- collider at SLAC, we search for the $h_b(1P)$ spin-singlet partner of the P-wave chi_{bJ}(1P) states in the sequential decay Upsilon(3S) --> pi0 h_b(1P), h_b(1P) --> gamma eta_b(1S). We observe an excess of events above background in the distribution of the recoil mass against the pi0 at mass 9902 +/- 4(stat.) +/- 2(syst.) MeV/c^2. The width of the observed signal is consistent with experimental resolution, and its significance is 3.1sigma, including systematic uncertainties. We obtain the value (4.3 +/- 1.1(stat.) +/- 0.9(syst.)) x 10^{-4} for the product branching fraction BF(Upsilon(3S)-->pi0 h_b) x BF(h_b-->gamma eta_b).Comment: 8 pages, 4 postscript figures, submitted to Phys. Rev. D (Rapid Communications