Muon Data Research Articles

The CMS L1 Trigger emulation software

The CMS L1 Trigger processes the muon and calorimeter detector data using a complex system of custom hardware processors. A bit-level emulation of the trigger data processing has been developed. This is used to validate and monitor the trigger hardware, to simulate the trigger response in monte-carlo data, and for some components, to seed higher-level triggers. The multiple-use cases are managed using a modular design, implemented within the modular CMS offline software framework. The requirements, design and performance of the emulators are described, as well as the iterative process required to bring the emulators and hardware into agreement.

Calibration of the barrel muon drift tubes system in CMS

In this report, results on the calibration process of the Drift Tubes (DT) system of the Compact Muon Solenoid experiment are presented. The full commissioning of the calibration procedure has been deployed in year 2008 with the CMS Computing, Software and Analysis challenge (CSA08), which has tested the full work-flow needed for CMS data-taking during the LHC start-up operations. In autumn 2008, the same Calibration work-flow was applied to a high statistics cosmic ray muon data taking period: the Cosmic Run At Four Tesla (CRAFT) period. The accurate measurement of the main calibration conditions corresponding to the Time Pedestals and the Drift Velocity provide the necessary space-time relationship used in the first stage of the muon local reconstruction.

Commissioning and first data with the ATLAS silicon microstrip tracker

The ATLAS experiment at the CERN large hadron collider (LHC) has started taking data this autumn with the inauguration of the LHC. The semiconductor tracker (SCT) is the key precision tracking device in ATLAS, made up from silicon micro-strip detectors processed in the planar p-in-n technology.The completed SCT has recently been installed inside the ATLAS experimental hall. Quick tests were performed last year to verify the connectivity of the electrical and optical services. Problems observed with the heaters for the evaporative cooling system have been resolved. This has enabled extended operation of the full detector under realistic conditions. Calibration data has been taken and analysed to determine the noise performance of the system. In addition, extensive commissioning with cosmic ray events has been performed. The cosmic muon data has been used to align the detector, to check the timing of the front-end electronics as well as to measure the hit efficiency of modules.The current status of the SCT will be reviewed, including results from the latest data-taking periods in autumn 2008, and from the detector alignment. We will report on the commissioning of the detector, including overviews on services, connectivity and observed problems. Particular emphasis will also be placed on the SCT data taken in the latest running period with the entire ATLAS detector participating. The SCT commissioning and running experience will then be used to extract valuable lessons for future silicon strip detector projects.

Performance of the ATLAS liquid argon calorimeter with cosmic muons and single LHC beam data

The Liquid Argon (LAr) calorimeter is a key detector in the ATLAS (A Toroidal LHC ApparatuS) experiment at the Large Hadron Collider (LHC), designed to provide precision measurements of electrons, photons, jets and missing transverse energy. Cosmic muon data has been recorded by the LAr calorimeter at various stages of commissioning, with the first single LHC beam data being recorded in September 2008. We present here the LAr calorimeter performance studies based on cosmic muons and LHC beam data. In 2008, ∼99% of the LAr readout channels were fully operational. The high energy deposits in the calorimeter readout cells have been used to validate the signal shape reconstruction from calibration predictions at a level better than ∼2%. The measured timing alignment agrees with expectations at the 2ns level. The non-uniformity of the barrel electromagnetic (EM) calorimeter has been estimated less than 2% thanks to cosmic muons.

The CMS silicon strip tracker performance using cosmic ray data

The CMS Silicon Strip Tracker (SST) is the largest tracking system based on silicon detector technology ever built for high energy physics experiments. It consists of 24,244 single-sided micro-strip sensors for a total active area of 198m2 and about 9.3 million readout channels. The detector was installed inside CMS in December 2007, commissioned during summer 2008 and then it participated along with other subdetector components of CMS in cosmic muons data taking runs. The commissioning strategy, the operational experience and the detector performance results are presented.

Identification and filtering of uncharacteristic noise in the CMShadron calorimeter

Commissioning studies of the CMS hadron calorimeter have identified sporadic uncharacteristic noise and a small number of malfunctioning calorimeter channels. Algorithms have been developed to identify and address these problems in the data. The methods have been tested on cosmic ray muon data, calorimeter noise data, and single beam data collected with CMS in 2008. The noise rejection algorithms can be applied to LHC collision data at the trigger level or in the offline analysis. The application of the algorithms at the trigger level is shown to remove 90% of noise events with fake missing transverse energy above 100 GeV, which is sufficient for the CMS physics trigger operation.

Absence of magnetic phase separation in MnSi under pressure

We report muon spin spectroscopy data (muSR) obtained under hydrostatic pressure on a large single crystal of the itinerant helimagnet MnSi, and recorded down to 0.235 K and up to 15.1 kbar. Up to the critical pressure p_c = 14.9 (2) kbar, where the magnetic order is suppressed, the muSR data unambiguously demonstrate that the ground state of the system is magnetic with no indication of any phase separation.

The Data Quality Monitoring of the CMS Experiment: the Tracker Case

The Data Quality Monitoring system in the CMS experiment has been designed for the monitoring of both the online data taking as well as offline data processing, such as reconstruction of data at Tier0. The goal of the online DQM system is to monitor detector performance and identify problems efficiently and with small latency during the data collection. On the other hand the reconstruction or calibration problems can be detected during offline processing using the same tool. The monitoring is performed with histograms which are filled by accessing information from raw and reconstructed data. We shall describe the CMS Data Quality Monitoring system in general with special emphasis on its application to the monitoring of the CMS Silicon Strip Track detector. Experience with the system from the cosmic ray muon data taking, before the installation of the tracking detector in the underground CMS experiment as well as during the global runs after completion of the detector installation, will be reported.

First results on the CMS RPC system using the 2007 and 2008 cosmic ray data

A preliminary study of the performance of the CMS RPC system will be here presented. A large set of muons have been triggered and reconstructed using cosmic ray data taken in the 2007 and 2008 CMS Global Runs. The Drift Tube chambers and the RPC chambers have both been used as trigger system and the data have been used to measure detector and trigger performances. RPC detector and trigger efficiencies have been measured using muon data triggered by DT chambers only in order to have an unbiased set of data. More studies on the RPC detector have been performed (noise, current, cluster size) and the first results will also be shown here.

Commissioning the ATLAS Silicon Microstrip Tracker

The completed SemiConductor Tracker (SCT) has been installed inside ATLAS. Tests were performed last year to verify the connectivity of the electrical and optical services. Problems observed with the heaters for the evaporative cooling system have been resolved. This has enabled extended operation of the full detector under realistic conditions. Calibration data has been taken and analyzed to determine the noise performance of the system. In addition, extensive commissioning with cosmic ray events has started. The cosmic muon data has been used to align the detector, to check the timing of the front-end electronics as well as to check hit efficiency of modules. The current status of the SCT will be reviewed.

Primary cosmic ray energy spectrum in terms of the GAMMA muon data

The energy spectrum of the primary cosmic rays is obtained by conversion from the truncated muon size spectrum of EAS studied with the GAMMA array. The previously observed dependence of E 0 on N μ tr at various zenith angles is used. It is shown that the present spectrum has the same structure (“bump”) as the spectrum determined by another independent multi-parametric energy estimation method confirming that the “bump” structure is not produced by uncertainties in our methods.

The Constant Intensity Cut Method applied to the KASCADE-Grande muon data

The constant intensity cut method is a very useful tool to reconstruct the cosmic ray energy spectrum in order to combine or compare extensive air shower data measured for different attenuation depths independently of the MC model. In this contribution the method is used to explore the muon data of the KASCADE-Grande experiment. In particular, with this technique, the measured muon number spectra for different zenith angle ranges are compared and summed up to obtain a single muon spectrum for the measured showers. Preliminary results are presented, along with estimations of the systematic uncertainties associated with the analysis technique.

Commissioning and performance of the ATLAS Inner Detector with the first beam and cosmic data

The ATLAS experiment at the CERN Large Hadron Collider (LHC) started data-taking in Autumn 2008 with the inauguration of the LHC. The Inner Detector is a tracking system for charged particles based on three technologies: silicon pixels, silicon micro-strips and drift tubes. The detector was commissioned and calibrated in the ATLAS cavern. Cosmic muons data are used for timing the different components of the system, measuring detector performance on particles and cross-checking the calibration results. Cosmic ray data serve also to align the detector prior to the LHC start up, exercising the alignment procedure to be repeated during the accelerator's operation. Tracking performance after this early alignment is suitable for initial LHC collisions.

Commissioning of the ATLAS liquid argon calorimeter

The in situ commissioning of the ATLAS liquid argon calorimeter is taking place since three years. During this period, it has been fully tested by means of frequent calibration runs, and the analysis of the large cosmic muon data samples and of the few beam splash events that occurred on September 10th, 2008. This has allowed to obtain a stable set of calibration constants for the first collisions, and to measure the in situ calorimeter performances that were found to be at the expected level.

SEARCH FOR ASTROPHYSICAL NEUTRINO POINT SOURCES AT SUPER-KAMIOKANDE

It has been hypothesized that large fluxes of neutrinos may be created in astrophysical "cosmic accelerators." The primary background for a search for astrophysical neutrinos comes from atmospheric neutrinos, which do not exhibit the pointlike directional clustering that characterizes a distant astrophysical signal. We perform a search for neutrino point sources using the upward-going muon data from three phases of operation (SK-I, SK-II, and SK-III) spanning 2623 days of live time taken from April 1, 1996 to August 11, 2007. The search looks for signals from suspected galactic and extragalactic sources, transient sources, and unexpected sources. We find interesting signatures from two objects--RX J1713.7-3946 (97.5% CL) and GRB 991004D (95.3% CL)--but the signatures lack compelling statistical significance given trial factors. We set limits on the flux and fluence of neutrino point sources above energies of 1.6 GeV.

Statistical Image Reconstruction for Muon Tomography Using a Gaussian Scale Mixture Model

Muon tomography is a novel imaging technique that uses background cosmic radiation to inspect vehicles or cargo containers for detecting the transportation or smuggling of heavy nuclear materials. Empirically, muon scattering data are modeled as zero-mean Gaussian random variables with variance being a function of the atom number and density of the scattering material. However, a single Gaussian distribution cannot model the tail of the true distribution and hence results in noisy reconstructed images. In this paper, we propose a Gaussian scale mixture (GSM) to approximate the true distribution of muon data. The GSM follows the true distribution more closely than a single Gaussian model. We have derived a maximum a posteriori (MAP) reconstruction algorithm based on the GSM likelihood. Localization receiver operating characteristics (LROC) studies were performed using computer simulated data to evaluate the new algorithm. The results show that the use of GSM improves the detection performance significantly over that of the traditional Gaussian likelihood.

Symmetry of the spin Hamiltonian for herbertsmithite: A spin-12kagome lattice

We present magnetization measurements on oriented powder of ${\text{ZnCu}}_{3}{(\text{OH})}_{6}{\text{Cl}}_{2}$ along and perpendicular to the orienting field. We find a dramatic difference in the magnetization between the two directions. It is biggest at low measurement fields $H$ or high temperatures. We show that the difference at high temperatures must emerge from the Ising-type exchange anisotropy. This allows us to explain muon spin rotation data at $T\ensuremath{\rightarrow}0$ in terms of an exotic ferromagnetic ground state.

Commissioning the ATLAS silicon microstrip tracker

The completed SemiConductor Tracker (SCT) has been installed inside ATLAS. Quick tests were performed last year to verify the connectivity of the electrical and optical services. Problems observed with the heaters for the evaporative cooling system have been resolved. This has enabled extended operation of the full detector under realistic conditions. Calibration data has been taken and analyzed to determine the noise performance of the system. In addition, extensive commissioning with cosmic ray events has started. The cosmic muon data has been used to align the detector, to check the timing of the front-end electronics as well as to measure the hit efficiency of modules. The current status of the SCT will be reviewed, including results from the latest data-taking periods. The commissioning experience will be used to extract lessons for future silicon detector projects.

Sudden stratospheric warmings seen in MINOS deep underground muon data

The rate of high energy cosmic ray muons as measured underground is shown to be strongly correlated with upper‐air temperatures during short‐term atmospheric (10‐day) events. The effects are seen by correlating data from the MINOS underground detector and temperatures from the European Centre for Medium Range Weather Forecasts during the winter periods from 2003–2007. This effect provides an independent technique for the measurement of meteorological conditions and presents a unique opportunity to measure both short and long‐term changes in this important part of the atmosphere.

Precision measurement of the muon decay parametersρandδ

The TWIST Collaboration has performed new measurements of two of the parameters that describe muon decay: ρ, which governs the shape of the overall momentum spectrum, and δ, which governs the momentum dependence of the parity-violating decay asymmetry. This analysis gives the results ρ=0.750 14±0.000 17(stat)±0.000 44(syst)±0.000 11(η), where the last uncertainty arises from the correlation between ρ and the decay parameter η, and δ=0.750 67±0.000 30(stat)±0.000 67(syst). These are consistent with the value of 3/4 given for both parameters in the standard model of particle physics, and are a factor of two more precise than the measurements previously published by TWIST. A new global analysis of all available muon decay data incorporating these results is presented. Improved lower and upper limits on the decay parameter Pμπξ of 0.995 24<Pμπξ≤ξ<1.000 91 at 90% confidence are determined, where Pμπ is the polarization of the muon when it is created during pion decay, and ξ governs the muon decay asymmetry. These results set new model-independent constraints on the possible weak interactions of right-handed particles. Specific implications for left-right symmetric models are discussed.7 MoreReceived 7 July 2008DOI:https://doi.org/10.1103/PhysRevD.78.032010This article is available under the terms of the Creative Commons Attribution 3.0 License. Further distribution of this work must maintain attribution to the author(s) and the published article’s title, journal citation, and DOI.