Antonio Vilela Pereira

We present the FP420 R&D project, which has been studying the key aspects of the development and installation of a silicon tracker and fast-timing detectors in the LHC tunnel at 420 m from the interaction points of the ATLAS and CMS experiments. These detectors would measure precisely very forward protons in conjunction with the corresponding central detectors as a means to study Standard Model (SM) physics, and to search for and characterise new physics signals. This report includes a detailed description of the physics case for the detector and, in particular, for the measurement of Central Exclusive Production, pp→p+ϕ+p, in which the outgoing protons remain intact and the central system ϕ may be a single particle such as a SM or MSSM Higgs boson. Other physics topics discussed are γγ and γp interactions, and diffractive processes. The report includes a detailed study of the trigger strategy, acceptance, reconstruction efficiencies, and expected yields for a particularpp→pHp measurement with Higgs boson decay in theb mode. The document also describes the detector acceptance as given by the LHC beam optics between the interaction points and the FP420 location, the machine backgrounds, the new proposed connection cryostat and the moving (``Hamburg'') beam-pipe at 420 m, and the radio-frequency impact of the design on the LHC. The last part of the document is devoted to a description of the 3D silicon sensors and associated tracking performances, the design of two fast-timing detectors capable of accurate vertex reconstruction for background rejection at high-luminosities, and the detector alignment and calibration strategy.

We present measurements of the reduction of light output by plastic scintillators irradiated in the CMS detector during the 8 TeV run of the Large Hadron Collider and show that they indicate a strong dose rate effect. The damage for a given dose is larger for lower dose rate exposures. The results agree with previous measurements of dose rate effects, but are stronger due to the very low dose rates probed. We show that the scaling with dose rate is consistent with that expected from diffusion effects.

The first search for the Z boson decay to $\tau\tau\mu\mu$ at the CERN LHC is presented, based on data collected by the CMS experiment at the LHC in proton-proton collisions at a center-of-mass energy of 13 TeV and corresponding to an integrated luminosity of 138 fb$^{-1}$. The data are compatible with the predicted background. For the first time, an upper limit at the 95% confidence level of 6.9 times the standard model expectation is placed on the ratio of the Z $\to$ $\tau\tau\mu\mu$ to Z $\to$ 4$\mu$ branching fractions. Limits are also placed on the six flavor-conserving four-lepton effective-field-theory operators involving two muons and two tau leptons, for the first time testing all such operators.

The absorption spectrum of CalCl in the region 2840–2980 Å has been generated using a King furnace. Seven bands belonging to the E2Σ-X2Σ transition have been rotationally analyzed and molecular constants have been evaluated.

The CMS pixel detector is the innermost tracking device at the LHC, reconstructing interaction vertices and charged particle trajectories. The current planar sensors located in the innermost layer of the pixel detector will be exposed to very high fluences which will degrade their performances. As a possible replacement for planar pixel sensors in the High Luminosity-LHC (HL-LHC), 3D silicon technology is under consideration due to its expected good performance in harsh radiation environments. Studies are also in progress for using 3D silicon pixel detectors in near-beam proton spectrometers at the LHC. Deep Reactive Ion Etching (DRIE) plays a key role in fabricating 3D silicon detectors in which readout and ohmic electrodes are processed through the silicon substrate instead of being implanted on the silicon surface. 3D pixel devices considered in this study were processed at FBK (Trento, Italy), bump bonded to the CMS pixel readout chip, and characterized in the laboratory. Numerical simulations were also carried out. We report on selected results from laboratory measurements and TCAD simulations.

We study hard diffractive scattering in hadron–hadron collisions including, on top of the standard Pomeron-initiated processes, contributions due to the exchange of Reggeons. Using a simple model to describe the parton content of the Reggeon, we compute di-jet production in single diffractive and central diffractive events. We show that Reggeon contributions can be sizable at the LHC, and even sometimes dominant, and we identify kinematic windows in which they could be experimentally studied. We argue that suitable measurements must be performed in order to properly constrain the model, and be able to correctly account for Reggeon exchanges in the analysis of the many hard diffractive observables to be measured at the LHC.

Transitions in the C 2Π-X 2Σ green band system of gaseous BaCl were excited by different Ar+ and Kr+ laser lines, and the induced fluorescence was photographed in high resolution. The emission spectrum, produced by a hollow cathode lamp, was recorded and the band heads measured with high accuracy. Using the spectral information and recently published values for the ground state rotational constants, vibrational and rotational analyses were performed. The vibrational constants obtained for the ground state of the 138Ba35Cl molecule are (in cm-1) ωe = 279.89, ωexe = 0.802 and ωeye = 3.3 × 10-4. The following main molecular equilibrium constants for the C 2Π state were derived (in cm-1):

In preparation for the tenfold luminosity upgrade of the Large Hadron Collider (the HL-LHC) around 2020, three-dimensional (3D) silicon pixel sensors are being developed as a radiation-hard candidate to replace the planar ones currently being used in the CMS pixel detector. This study examines an early batch of FBK sensors (named ATLAS08) of three 3D pixel geometries: 1E, 2E, and 4E, which respectively contain one, two, and four readout electrodes for each pixel, passing completely through the bulk. We present electrical characteristics and beam test performance results for each detector before and after irradiation. The maximum fluence applied is 3.5×1015 n eq/cm2.

The blue-green band system of gaseous Pb2 was excited by different Ar+ laser lines. The dense structure of the bands and the fact that natural lead has several isotopes leads to numerous fluorescence series for each exciting line even for narrow laser lines. The fluorescence progressions, which consist of close doublets, were photographed in a 3 m concave grating spectrograph with a resolving power of 180 000. The observed intensities were compared with computed Franck-Condon factors in order to ascertain the vibrational analysis. From observed lines due to rotational relaxation with known change of angular momentum and using isotope relations a set of simultaneous equations that included many fluorescence progressions was built up and a complete rotational and vibrational analysis could be carried out. In the final analysis the ν' numbers range from 0 up to 22, the ν" numbers from 0 up to 19 and the J' numbers up to 306. The first vibrational and rotational constants for the 208Pb2 molecule are (in cm-1) for the lower state:

The absorption spectrum of gaseous CaCl in the wavelength region 2990-3300 Å has been studied using a King furnace. Ten bands belonging to the D 2 Σ- X 2 Σ transition have been analyzed and both vibrational and rotational constants have been evaluated. The following molecular constants have been determined (cm -1 ): X 2 Σ D 2 Σ T e 0.0 31 110.934(5) ω e 370.201 423.254(7) ω e x e 1.3732 1.581(3) ω e y e 9.3 × 10 -3 1.6(4) × 10 -3 ω e z e -4.8 × 10 -4 -2.9(2) × 10 -4 B e 0.152 233 0.162 975 4(8) α e 7.92 × 10 -4 7.968(2) × 10 -4 D e 1.068 × 10 -7 1.0090(3) × 10 -7 γ e 1.38 × 10 -3 1.2 × 10 -3 The figures in parentheses stand for one standard deviation in the last digit for the computed quantity.

The barrel region of the Compact Muon Solenoid (CMS) experiment at the Large Hadron Collider is instrumented with Drift Tube (DT) detectors. This paper describes in full details the calibration of the DT hit reconstruction algorithm. After inter-channel synchronization has been verified through the appropriate hardware procedure, the time pedestals are extracted directly from the distribution of the recorded times. Further corrections for time-of-flight and time of signal propagation are applied as soon as the three-dimensional hit position within the DT chamber is known. The different effects of the time pedestal miscalibration on the two main hit reconstruction algorithms are shown. The drift velocity calibration algorithm is based on the meantimer technique. Different meantimer relations for different track angles and patterns of hit cells are used. This algorithm can also be used to determine the uncertainty on the reconstructed hit position.

Three-dimensional (3D) silicon detectors are emerging as one of the most promising technologies for the innermost layers of tracking devices for the foreseen upgrades of the LHC. 3D sensors compatible with the CMS readout, fabricated at FBK (Trento, Italy), were tested in the laboratory and with a 120 GeV/c proton beam at the FNAL test beam facility, before and after irradiation up to a fluence of 3.5×1015neq/cm2. Preliminary results of the data analysis are presented.

Abstract Silicon 3D detectors consist of an array of columnar electrodes of both doping types which penetrate entirely in the detector bulk, perpendicularly to the surface. They are emerging as one of the most promising technologies for innermost layers of tracking devices for the foreseen upgrades of the LHC. Until recently, properties of 3D sensors have been investigated mostly with ATLAS readout electronics. 3D pixel sensors compatible with the CMS readout were first fabricated at SINTEF (Oslo, Norway), and more recently at FBK (Trento, Italy) and CNM (Barcelona, Spain). Several sensors with different electrode configurations, bump-bonded with the CMS pixel PSI46 readout chip, were characterized in laboratory and tested at Fermilab with a proton beam of 120 GeV/ c . Preliminary results of the data analysis are presented.

A high resolution spectrum of the C2Π-X2Σ system of CaCl has been recorded in absorption. A rotational analysis is presented and molecular constants are evaluated.

We study the light output, light collection efficiency and signal timing of a variety of organic scintillators that are being considered for the upgrade of the hadronic calorimeter of the CMS detector. The experimental data are collected at the H2 test-beam area at CERN, using a 150 GeV muon beam. In particular, we investigate the usage of over-doped and green-emitting plastic scintillators, two solutions that have not been extensively considered. We present a study of the energy distribution in plastic-scintillator tiles, the hit efficiency as a function of the hit position, and a study of the signal timing for blue and green scintillators.

A simulation for the existence of particles and couplings, that are not predicted in the Standard Model (SM), can be performed by evaluating the contributions of anomalous photon-gauge boson couplings to W and Z pair production in proton-proton collisions at the LHC.In this work, we present our preliminary results for Z pair exclusive production from two-photon exchange with anomalous gauge boson quartic couplings, by considering a 1 TeV scale for new physical effects.We consider some values for the integrated luminosity up to 100 fb -1 at center-of-mass energy of 13 TeV.We calculate the total cross section for the exclusive process and we present the resulting four lepton invariant mass distribution.Finally we present an outlook for the present analysis.

Views Icon Views Article contents Figures & tables Video Audio Supplementary Data Peer Review Share Icon Share Twitter Facebook Reddit LinkedIn Tools Icon Tools Reprints and Permissions Cite Icon Cite Search Site Citation Antonio Vilela Pereira, CMS Collaboration; Soft and hard diffraction with CMS. AIP Conf. Proc. 28 September 2012; 1441 (1): 184–186. https://doi.org/10.1063/1.3700507 Download citation file: Ris (Zotero) Reference Manager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentAIP Publishing PortfolioAIP Conference Proceedings Search Advanced Search |Citation Search

Views Icon Views Article contents Figures & tables Video Audio Supplementary Data Peer Review Share Icon Share Twitter Facebook Reddit LinkedIn Tools Icon Tools Reprints and Permissions Cite Icon Cite Search Site Citation Antonio Vilela Pereira, The CMS collaboration; Diffraction with CMS. AIP Conference Proceedings 15 July 2011; 1350 (1): 160–163. https://doi.org/10.1063/1.3601398 Download citation file: Ris (Zotero) Reference Manager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentAIP Publishing PortfolioAIP Conference Proceedings Search Advanced Search |Citation Search

The Phase I upgrade of the CMS Hadron Endcap Calorimeters consists of new photodetectors (Silicon Photomultipliers in place of Hybrid Photo-Diodes) and front-end electronics. The upgrade will eliminate the noise and the calibration drift of the Hybrid Photo-Diodes and enable the mitigation of the radiation damage of the scintillators and the wavelength shifting fibers with a larger spectral acceptance of the Silicon Photomultipliers. The upgrade also includes increased longitudinal segmentation of the calorimeter readout, which allows pile-up mitigation and recalibration due to depth-dependent radiation damage. As a realistic operational test, the responses of the Hadron Endcap Calorimeter wedges were calibrated with a 60Co radioactive source with upgrade electronics. The test successfully established the procedure for future source calibrations of the Hadron Endcap Calorimeters. Here we describe the instrumentation details and the operational experiences related to the sourcing test.

The PPS (Precision Proton Spectrometer) detector system consists of silicon tracking stations as well as timing detectors to measure both the position and direction of protons and their time-of-flight with high precision. They are located at around $200\textrm{-}220\,\textrm{m}$ from the interaction point in the very forward region on both sides of the CMS experiment. The PPS detector is built to study central exclusive production (CEP) in proton-proton collisions at the LHC, including the photon-photon production of W and Z boson pairs, high-mass photon and lepton pairs, high-$p_T$ jet production, as well as searches for anomalous couplings and new resonances. The PPS detector system has taken data at high luminosity while fully integrated to the CMS experiment. The total data collected correspond to around $100\,{\rm fb}^{-1}$ during the LHC Run 2, from 2016-2018. For the first time, exclusive production of lepton pairs has been observed in the CMS detector while one outgoing proton is measured in PPS using roughly $10\,{\rm fb}^{-1}$ of data accumulated in 2016 during high-luminosity LHC operation. These first results show a good understanding, calibration and alignment of the PPS detectors.

The absorption spectrum of gaseous Pb 2 has been investigated in the blue – green spectral region. Owing to the overlap between the six dominating isotopic Pb 2 molecules formed by natural lead – in combination with the very dense structure of the [Formula: see text] transition – it is impossible to rotationally resolve the Doppler limited spectrum. Still, regions of rotational structure were resolved. These were explained by interference effects between the absorption spectra of the individual isotopic species. The regions of resolved rotational structure form a pattern similar to a moiré pattern. The information gained is used together with laser induced fluorescence data in a reanalysis of the F and X states. The following main molecular constants for the 208 Pb 2 molecule have been derived (cm −1 ):[Formula: see text]