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CMS Notes

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2017-10-20
16:53
Test beam demonstration of silicon microstrip modules with transverse momentum discrimination for the future CMS tracking detector / Abbaneo, Duccio (CERN) ; Auzinger, Georg (Imperial Coll., London) ; Bergauer, Thomas (Vienna, OAW) ; Georges Blanchot ; Bonnin, Christian (Strasbourg, IPHC) ; Braga, Davide (Rutherford) ; Charles, Laurent (Strasbourg, IPHC) ; Roy Chowdhury, Suvankar (Saha Inst.) ; Cussans, David (Bristol U.) ; Delaere, Christophe (Louvain U.) et al.
A new CMS Tracker is under development for operation at the High Luminosity LHC from 2026 onwards. It includes an outer tracker based on dedicated modules that will reconstruct short track segments, called stubs, using spatially coincident clusters in two closely spaced silicon sensor layers. These modules allow the rejection of low transverse momentum track hits and reduce the data volume before transmission to the first level trigger. The inclusion of tracking information in the trigger decision is essential to limit the first level trigger accept rate. A customized front-end readout chip, the CMS Binary Chip (CBC), containing a stub finding logic has been designed for this purpose. A prototype module, equipped with the CBC chip, has been constructed and operated for the first time in a $4\,\text{Ge\hspace{-.08em}V\hspace{-0.16em}/\hspace{-0.08em}}c$ positron beam at DESY. The behaviour of the stub finding was studied for different angles of beam incidence on a module, which allows an estimate of the sensitivity to transverse momentum within the future CMS detector. A sharp transverse momentum threshold around $2\,\text{Ge\hspace{-.08em}V\hspace{-0.16em}/\hspace{-0.08em}}c$ was demonstrated, which meets the requirement to reject a large fraction of low momentum tracks present in the LHC environment on-detector. This is the first realistic demonstration of a silicon tracking module that is able to select data, based on the particle's transverse momentum, for use in a first level trigger at the LHC. The results from this test are described here..
CMS-NOTE-2017-010; CERN-CMS-NOTE-2017-010.- Geneva : CERN, 2016 - 27 p. Fulltext: PDF;

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2017-10-09
10:39
An FPGA-Based Track Finder for the L1 Trigger of the CMS Experiment at the High Luminosity LHC / Aggleton, Robin Cameron (Hamburg U.) ; Ardila Perez, Luis Eduardo (KIT, Karlsruhe, EKP) ; Ball, Fionn Amhairghen (Bristol U.) ; Balzer, Matthias Norbert (KIT, Karlsruhe, EKP) ; Boudoul, Gaelle (Lyon, IPN) ; Brooke, James John (Bristol U.) ; Caselle, Michele (KIT, Karlsruhe, EKP) ; Calligaris, Luigi (Rutherford) ; Cieri, Davide (Rutherford) ; Clement, Emyr John (Bristol U.) et al.
A new tracking detector is under development for use by the CMS experiment at the High-Luminosity LHC (HL-LHC). A crucial requirement of this upgrade is to provide the ability to reconstruct all charged particle tracks with transverse momentum above 2--3\ GeV within 4$\mu$s so they can be used in the Level-1 trigger decision. A concept for an FPGA-based track finder using a fully time-multiplexed architecture is presented, where track candidates are reconstructed using a projective binning algorithm based on the Hough Transform, followed by a combinatorial Kalman Filter. [...]
CMS-NOTE-2017-009; CERN-CMS-NOTE-2017-009.- Geneva : CERN, 2017 - 41 p. Fulltext: PDF;

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2017-09-15
11:43
Characterisation of Irradiated Thin Silicon Sensors for the CMS Phase II Pixel Upgrade / Centis Vignali, Matteo (Hamburg U.) ; Eckstein, Doris (DESY) ; Eichhorn, Thomas (DESY) ; Garutti, Erika (Hamburg U.) ; Junkes, Alexandra (Hamburg U.) ; Steinbrueck, Georg (Hamburg U.) ; bigskip ; Institut fur Experimentalphysik ; Luruper Chaussee ; Hamburg et al.
The high luminosity upgrade of the Large Hadron Collider, foreseen for 2025, necessitates the replacement of the CMS experiment's silicon tracker. The innermost layer of the new pixel detector will be exposed to severe radiation, corresponding to a 1 MeV neutron equivalent fluence of up to $\Phi_{eq} = 2 \times 10^{16}$ cm$^{-2}$, and an ionising dose of $\approx 5$ MGy after an integrated luminosity of 3000 fb$^{-1}$. Thin, planar silicon sensors are good candidates for this application, since the degradation of the signal produced by traversing particles is less severe than for thicker devices. In this paper, the results obtained from the characterisation of 100 and 200\,$\mu$m thick p-bulk pad diodes and strip sensors irradiated up to fluences of $\Phi_{eq} = 1.3 \times 10^{16}$ cm$^{-2}$ are shown..
CMS-NOTE-2017-008; CERN-CMS-NOTE-2017-008.- Geneva : CERN, 2016 - 17 p. Fulltext: PDF;

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2017-09-11
11:10
The drift velocity monitoring system of the CMS barrel muon chambers / Altenhoefer, Georg Friedrich (Aachen, Tech. Hochsch.) ; Hebbeker, Thomas (Aachen, Tech. Hochsch.) ; Heidemann, Carsten Andreas (Aachen, Tech. Hochsch.) ; Reithler, Hans (Aachen, Tech. Hochsch.) ; Sonnenschein, Lars (Aachen, Tech. Hochsch.) ; Teyssier, Daniel Francois (Aachen, Tech. Hochsch.)
The drift velocity is a key parameter of drift chambers. Its value depends on several parameters: electric field, pressure, temperature, gas mixture, and contamination, for example, by ambient air. [...]
CMS-NOTE-2017-007; CERN-CMS-NOTE-2017-007.- Geneva : CERN, 2017 - 16 p. Fulltext: PDF;

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2017-06-22
17:07
Thin Double-gap RPCs for the Phase-2 Upgrade of the CMS Muon System / Lee, Kyong Sei (Korea U.) ; Park, Sung Keun (Korea U.)
High-sensitive double-gap phenolic Resistive Plate Chambers are studied for the Phase-2 upgrade of the CMS muon system at high pseudorapidity $\eta$. Whereas the present CMS RPCs have a gas gap thickness of 2 mm, we propose to use thinner gas gaps, which will improve the performance of these RPCs. [...]
CMS-NOTE-2017-006; CERN-CMS-NOTE-2017-006.- Geneva : CERN, 2017 - 10 p. Fulltext: PDF;

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2017-06-22
11:22
Thin Double-gap RPCs for the Phase-2 Upgrade of the CMS Muon System / Lee, Kyong Sei (Korea U.) ; Park, Sung Keun (Korea U.)
High-sensitive double-gap phenolic Resistive Plate Chambers are studied for the Phase-2 upgrade of the CMS muon system at high pseudorapidity $\eta$. Whereas the present CMS RPCs have a gas gap thickness of 2 mm, we propose to use thinner gas gaps, which will improve the performance of these RPCs. [...]
CMS-NOTE-2017-005; CERN-CMS-NOTE-2017-005.- Geneva : CERN, 2017 - 10 p. Fulltext: PDF;

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2017-06-06
10:17
Object definitions for top quark analyses at the particle level / CMS Collaboration /CMS Collaboration
The definition of the top quark at the particle level (pseudo-top) is discussed as a fundamental aspect of performing current and future measurements of differential production cross sections in both $\mathrm{t}\overline{\mathrm{t}}$ and single top quark production. Starting from initial studies performed in the context of the LHCtopWG, an optimization of the definition of pseudo-tops is proposed in order to maximize the correlation of the reconstructed quantities with the parton-level definition. The implementations and their optimization are performed using RIVET as a common framework to avoid the introduction of a dependence on a specific Monte Carlo event generator..
CMS-NOTE-2017-004; CERN-CMS-NOTE-2017-004.- Geneva : CERN, 2017 - 26 p. Fulltext: PDF;

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2017-05-09
10:50
P-Type Silicon Strip Sensors for the Future CMS Tracker / The Tracker Group of the CMS Collaboration /CMS Collaboration
The upgrade to the High-Luminosity LHC (HL-LHC) is expected to increase the LHC design luminosity by an order of magnitude. This will require silicon tracking detectors with a significantly higher radiation hardness. [...]
CMS-NOTE-2017-003; CERN-CMS-NOTE-2017-003.- Geneva : CERN, 2016 - 18 p. Fulltext: PDF;

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2017-05-09
10:50
Test Beam Performance Measurements for the Phase I Upgrade of the CMS Pixel Detector / Dragicevic, M. (Vienna, OAW) ; Friedl, M. (Vienna, OAW) ; Hrubec, J. (Vienna, OAW) ; Steininger, H. (Vienna, OAW) ; Gädda, A. (Helsinki Inst. of Phys.) ; Härkönen, J. (Helsinki Inst. of Phys.) ; Lampén, T. (Helsinki Inst. of Phys.) ; Luukka, P. (Helsinki Inst. of Phys.) ; Peltola, T. (Helsinki Inst. of Phys.) ; Tuominen, E. (Helsinki Inst. of Phys.) et al.
A new pixel detector for the CMS experiment is being built, owing to the instantaneous luminosities anticipated for the Phase I Upgrade of the LHC. The new CMS pixel detector provides four-hit tracking while featuring a reduced material budget as well as new cooling and powering schemes. [...]
CMS-NOTE-2017-002; arXiv:1706.00222; CERN-CMS-NOTE-2017-002.- Geneva : CERN, 2017-05-30 - 22 p. - Published in : JINST 12 (2017) P05022 Fulltext: openaccess_Dragicevic_2017_J._Inst._12_P05022 - PDF; NOTE2017_002 - PDF; Preprint: PDF;

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2017-01-24
10:03
Simplified likelihood for the re-interpretation of public CMS results / The CMS Collaboration /CMS Collaboration
In this note, a procedure for the construction of simplified likelihoods for the re-interpretation of the results of CMS searches for new physics is presented. The procedure relies on the use of a reduced set of information on the background models used in these searches which can readily be provided by the CMS collaboration. [...]
CMS-NOTE-2017-001; CERN-CMS-NOTE-2017-001.- Geneva : CERN, 2017 Fulltext: PDF;

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