General alignment concept of the CMS Lampén, T.
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
10/2006, Letnik:
566, Številka:
1
Journal Article
Recenzirano
Odprti dostop
Efficient and accurate track reconstruction requires proper alignment of the tracking devices used. Here, we describe the general alignment strategy envisaged for the CMS experiment. The hardware ...alignment devices of the CMS are presented as well as the different track-based alignment approaches.
The Silicon Beam Telescope (SiBT07) at the CERN H2 beam is a position-sensitive beam telescope targeted for LHC upgrade tests. The telescope consists of eight consecutive silicon microstrip detectors ...and slots for two test detectors. This article describes the reconstruction of reference tracks with the CMS data analysis software CMSSW. The related data analysis and calibration procedures, including pedestal corrections, common-mode corrections, and track-based alignment, are also described.
Silicon beam telescope for LHC upgrade tests Mäenpää, T.; Luukka, P.; Betchart, B. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
08/2008, Letnik:
593, Številka:
3
Journal Article
Recenzirano
A beam telescope based on the CMS Tracker data acquisition prototype cards has been developed in order to test sensor candidates for S-LHC tracking systems. The telescope consists of up to eight ...reference silicon microstrip modules and slots for a couple of test modules. Beam tracks, as measured by the reference modules, provide a means of determining the position resolution and efficiency of the test modules. The impact point precision of reference tracks at the location of the test modules is about
4
μ
m
. This note presents a detailed description of the silicon beam telescope (SiBT) along with some results from its initial operation in summer 2007 in the CERN H2 beamline.
The experience on using ROOT package TMVA for multivariate data analysis is reported for a problem of τ tagging in the framework of heavy charged MSSM Higgs boson searches at the LHC. We investigate ...with a generator level analysis how the τ tagging could be performed in an ideal case, and hadronic τ decays separated from the hadronic jets of QCD multi-jet background present in LHC experiments. A successful separation of the Higgs signal from the background requires a rejection factor of 105 or better against the QCD background. The τ tagging efficiency and background rejection are studied with various MVA classifiers.
Finnish CMS-TOB cosmic rack Mäenpää, T.; Hæggström, E.; Anttila, E. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
2007, Letnik:
570, Številka:
2
Journal Article
Recenzirano
Odprti dostop
We present a cosmic rack, the FinnCRack. This device is a silicon strip detector-based telescope that measures tracks of cosmic particles. The FinnCRack is constructed using components of the Tracker ...Outer Barrel (TOB) of the CMS experiment at the CERN LHC. The device is part of the TOB integration and verification effort together with its sister telescope, the CERN CRack. Both CRacks mimick a six degree slice of the TOB barrel structure. The FinnCRack is intended to (a) serve as a platform for TOB software development, both analysis and online software such as run control; (b) be used for noise and cluster shape studies; (c) act as a reference tracker in detector studies; and (d) provide a testbed for track-based alignment testing and development. The construction and setup of the FinnCRack have been documented in detail—the entire chain from connecting cables to physics data analysis—and the operation guide was tested in practice. Both these actions serve the purpose of training and attracting future HEP students. We also showed that we were able to measure cosmic muon tracks.
We test the usage of a Toolkit for Multivariate Data Analysis (TMVA) in b tagging. Tagging b jets associated with heavy neutral MSSM Higgs bosons at the LHC can be used to extract the Higgs bosons ...from the Drell-Yan background, for which the associated jets are mainly light quark and gluon jets. Achievable b tagging efficiency is studied with more than ten MVA classifiers at 1% mistagging rate. Most classifiers were found to perform better than the simple track counting algorithm.
Implementation of the CMS policy on long-term data preservation, re-use and open access has started. Current practices in providing data additional to published papers and distributing simplified ...data-samples for outreach are promoted and consolidated. The first measures have been taken for analysis and data preservation for the internal use of the collaboration and for open access to part of the data. Two complementary approaches are followed. First, a virtual machine environment, which will pack all ingredients needed to compile and run a software release with which the legacy data was reconstructed. Second, a validation framework, maintaining the capability not only to read the old raw data, but also to reprocess them with an updated release or to another format to help ensure long-term reusability of the legacy data.
Pad and strip detectors processed on high resistivity n-type magnetic Czochralski silicon (MCz-Si) were irradiated to several different fluences with protons. The pad detectors were characterized ...with the transient current technique (TCT) and the full-size strip detectors with a reference beam telescope and a 225
GeV muon beam. The TCT measurements indicate a double junction structure and space charge sign inversion in MCz-Si detectors after
6
×
10
14
1
MeV
n
eq
/
cm
2
fluence. In the beam test a signal-to-noise (
S/
N) ratio of 50 was measured for a non-irradiated MCz-Si sensor, and a
S/
N ratio of 20 for the sensors irradiated to the fluences of
1
×
10
14
1 and
5
×
10
14
1
MeV
n
eq
/
cm
2
.
Strip detectors with an area of
16
cm
2
were processed on high resistivity n-type magnetic Czochralski silicon. In addition, detectors were processed on high resistivity Float Zone wafers with the ...same mask set for comparison. The detectors were irradiated to several different fluences up to the fluence of
3
×
10
15
1
MeV
n
eq
/
cm
2
with protons or with mixed protons and neutrons. The detectors were fully characterized with CV- and IV-measurements prior to and after the irradiation. The beam test was carried out at the CERN H2 beam line using a silicon beam telescope that determines the tracks of the incoming particles and hence provides a reference measurement for the detector characterization. The n-type MCz-Si strip detectors have an acceptable
S/N at least up to the fluence of
1
×
10
15
n
eq
/
cm
2
and thus, they are a feasible option for the strip detector layers in the SLHC tracking systems.
A heavily irradiated (3×10
15 1
MeV
n
eq/cm
2) Current Injected Detector (CID) was tested with 225
GeV muon beam at CERN H2 beam line. In the CID concept the current is limited by the space charge. ...The injected carriers will be trapped by the deep levels and this induces a stable electric field through the entire bulk regardless of the irradiation fluence the detector has been exposed to. The steady-state density of the trapped charge is defined by the balance between the trapping and the emission rates of charge carriers (detrapping). Thus, the amount of charge injection needed for the electric field stabilization depends on the temperature. AC-coupled 16
cm
2 detector was processed on high resistivity n-type magnetic Czochralski silicon, and it had 768 strips, 50
μm pitch, 10
μm strip width and 3.9
cm strip length. The beam test was carried out using a silicon beam telescope that is based on the CMS detector readout prototype components, APV25 readout chips, and eight strip sensors made by Hamamatsu having 60
μm pitch and intermediate strips. The tested CID detector was bonded to the APV25 readout, and it was operated at temperatures ranging from −40 to −53
°C. The CID detector irradiated at 3×10
15 1
MeV
n
eq/cm
2 fluence shows about 40% relative Charge Collection Efficiency with respect to the non-irradiated reference plane sensors.
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