Laser monitoring system for the CMS lead tungstate crystal calorimeter

Anfreville, M.; Bailleux, D.; Bard, J-P.; Bornheim, A.; Bouchand, C.; Bougamont, E.; Boyer, M.; Chipaux, R.; Daponte-Puill, V.; Déjardin, M.; Faure, J.; Gras, P.; Jarry, P.; Jeanney, C.; Joudon, A.; Pansart, J. P.; Pénichot, Y.; Rander, J.; Rolquin, J.; Reymond, J. M.; Tartas, J.; Venault, Philippe; Verrecchia, P.; Zhang, L.; Zhu, K.; Zhu, R. Y.

doi:10.1016/j.nima.2008.01.104

Cited by 71 publications

(52 citation statements)

References 11 publications

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“…A dedicated monitoring system, based on the injection of laser light into each crystal, is used to track and correct for channel response changes caused by radiation damage and subsequent recovery of the crystals [37]. Response variations are a few percent in the barrel region, and increase up to a few tens of percent in the most-forward endcap regions.…”

Section: Jhep06(2013)081mentioning

confidence: 99%

Observation of a new boson with mass near 125 GeV in pp collisions at $ \sqrt{s}=7 $ and 8 TeV

Chatrchyan¹,

Khachatryan²,

Sirunyan³

et al. 2013

J. High Energ. Phys.

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554

427

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A detailed description is reported of the analysis used by the CMS Collaboration in the search for the standard model Higgs boson in pp collisions at the LHC, which led to the observation of a new boson. The data sample corresponds to integrated luminosities up to 5.1 fb −1 at √ s = 7 TeV, and up to 5.3 fb −1 at √ s = 8 TeV. The results for five Higgs boson decay modes γγ, ZZ, WW, τ τ , and bb, which show a combined local significance of 5 standard deviations near 125 GeV, are reviewed. A fit to the invariant mass of the two high resolution channels, γγ and ZZ → 4 , gives a mass estimate of 125.3 ± 0.4 (stat.) ± 0.5 (syst.) GeV. The measurements are interpreted in the context of the standard model Lagrangian for the scalar Higgs field interacting with fermions and vector bosons. The measured values of the corresponding couplings are compared to the standard model predictions. The hypothesis of custodial symmetry is tested through the measurement of the ratio of the couplings to the W and Z bosons. All the results are consistent, within their uncertainties, with the expectations for a standard model Higgs boson. The CMS collaboration 106 Keywords: Hadron-Hadron Scattering IntroductionThe standard model (SM) [1-3] of particle physics accurately describes many experimental results that probe elementary particles and their interactions up to an energy scale of a few hundred GeV [4]. In the SM, the building blocks of matter, the fermions, are comprised of quarks and leptons. The interactions are mediated through the exchange of force carriers: the photon for electromagnetic interactions, the W and Z bosons for weak interactions, and the gluons for strong interactions. All the elementary particles acquire mass through their interaction with the Higgs field [5][6][7][8][9][10][11][12][13]. This mechanism, called the "Higgs" or "BEH" mechanism [5][6][7][8][9][10], is the first coherent and the simplest solution for giving mass to W and Z bosons, while still preserving the symmetry of the Lagrangian. It is realized by introducing a new complex scalar field into the model. By construction, this field allows the W and Z bosons to acquire mass whilst the photon remains massless, and adds to the model one new scalar particle, the SM Higgs boson (H). The Higgs scalar field and its conjugate can also give mass to the fermions, through Yukawa interactions [11][12][13] The discovery or exclusion of the SM Higgs boson is one of the primary scientific goals of the LHC. Previous direct searches at the LHC were based on data from protonproton collisions corresponding to an integrated luminosity of 5.1 fb −1 collected at a centreof-mass energy of 7 TeV. The CMS experiment excluded at 95% CL masses from 127 to 600 GeV [20]. The ATLAS experiment excluded at 95% CL the ranges 111. . Within the remaining allowed mass region, an excess of events between 2 and 3 standard deviations (σ) near 125 GeV was reported by both experiments. In 2012, the proton-proton centre-of-mass energy was increased to 8 TeV, and by the end of June, an...

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Section: Jhep06(2013)081mentioning

confidence: 99%

Observation of a new boson with mass near 125 GeV in pp collisions at $ \sqrt{s}=7 $ and 8 TeV

Chatrchyan¹,

Khachatryan²,

Sirunyan³

et al. 2013

J. High Energ. Phys.

Self Cite

554

427

View full text Add to dashboard Cite

show abstract

“…In situ light transmission measurements are performed through a laser monitoring system which is based on injecting light into each crystal. The energy correction factor extracted by means of the laser monitoring system depends on the light collection mechanisms of both electromagnetic showers (S/S 0 ) and injected laser (R/R 0 ) [6]:…”

Section: Time Dependent Correctionsmentioning

confidence: 99%

Precision electromagnetic calorimetry at the energy frontier: The CMS ECAL at the LHC Run 2

Marzocchi¹

2016

Proceedings of the European Physical Society Conference on High Energy Physics — PoS(EPS-HEP2015)

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The Large Hadron Collider (LHC) has recently restarted operations (Run 2) with proton-proton collisions at an unprecedented centre-of-mass energy of 13 TeV and is moving to a reduced bunch spacing of 25 ns. After the successful quest for a Higgs boson via its electromagnetic decays, and the subsequent measurement of its mass, the CMS electromagnetic calorimeter (ECAL) plans to perform precision measurements and searches for new physics phenomena beyond the standard model with the data that are being collected. In this poster we present new reconstruction algorithms and calibration strategies that aim to maintain, and even improve, the excellent performance of the CMS ECAL under the new challenging experimental conditions. The CMS ECAL is a high-resolution, hermetic, and homogeneous electromagnetic calorimeter made of 75,848 scintillating lead tungstate crystals. Its resolution, as well as its timing performance, are valuable tools for the discovery of new physics with the CMS detector at the LHC. The performance of the calorimeter relies on precision calibration maintained over time, despite severe irradiation conditions. A set of intercalibration procedures using different physics channels is carried out at regular intervals to normalize the differences in crystal light transparency and photodetector response between channels, which can change due to accumulated radiation.

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“…While an intense R&D program led to the production of radiation resistant P bW O 4 crystals, a residual radiation damage remains and needs to be corrected for. Thus, the changes in transparency are measured by a dedicated laser monitoring system [5] (LM) which injects every 40 minutes a laser pulse (λ =440 nm, close to the peak of the scintillation light spectrum for P bW O 4 ) into each single crystal. The relative change in transparency (R/R 0 ) does not directly measures the relative change in response for the scintillation light (S/S 0 ) since the two have different spectra and the optical photons travel different paths to reach the photodetectors, but they can be related by a power law:…”

Section: Corrections For the Change Of The Response In Timementioning

confidence: 99%

The CMS electromagnetic calorimeter calibration during Run I: progress achieved and expectations for Run II

Ghezzi¹

2015

J. Phys.: Conf. Ser.

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Abstract.The CMS ECAL is a high-resolution, hermetic, and homogeneous electromagnetic calorimeter made of 75,848 scintillating lead tungstate crystals. It relies on precision calibration in order to achieve and maintain its design performance. A set of inter-calibration procedures is carried out to normalize the differences in crystal light yield and photodetector response between channels. Different physics channels such as low mass di-photon resonances, electrons from W and Z decays and the azimuthal symmetry of low energy deposits from minimum bias events are used. A laser monitoring system is used to measure and correct for response changes, which arise mainly from the harsh radiation environment at the LHC. The challenges of the different calibration techniques are discussed along with the performance evolution during Run I. The impact on physics performance is illustrated through the successful quest for the Higgs boson via its electromagnetic decays, and the subsequent mass measurement of the newly discovered particle. Conclusions are drawn for the performance to be expected from 2015 onwards, following the start of the LHC Run II.

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Laser monitoring system for the CMS lead tungstate crystal calorimeter

Cited by 71 publications

References 11 publications

Observation of a new boson with mass near 125 GeV in pp collisions at $ \sqrt{s}=7 $ and 8 TeV

Observation of a new boson with mass near 125 GeV in pp collisions at $ \sqrt{s}=7 $ and 8 TeV

Precision electromagnetic calorimetry at the energy frontier: The CMS ECAL at the LHC Run 2

The CMS electromagnetic calorimeter calibration during Run I: progress achieved and expectations for Run II

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