We apply the matrix element method (MEM) to the search for non-resonant Higgs boson pair (HH) production in the channel HH → bb̄WW* at the LHC and study the separation between the HH signal and the ...large irreducible background, which arises from the production of top quark pairs (tt̄). Our study focuses on events containing two leptons (electrons or muons) in the final state. The separation between signal and background is studied for experimental conditions characteristic for the ATLAS and CMS experiments during LHC Run 2, using the DELPHES fast-simulation package. We find that the tt̄ background can be reduced to a level of 0.26% for a signal efficiency of 35%.
The front-end electronics upgrade of the CMS ECAL barrel Cossio, Fabio
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
01/2023, Letnik:
1046
Journal Article
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The barrel part of the CMS electromagnetic calorimeter (ECAL) consists of 61200 PbWO4 crystals coupled to avalanche photodiodes (APDs). A decrease of the ECAL operating temperature from 18 °C to 9 °C ...is needed to mitigate the increase in APD noise from radiation-induced dark current in the conditions of the high luminosity upgrade of the LHC. Moreover, a full re-design of the front-end electronics has been undertaken in order to deal with the increase of pileup events and to improve the rejection of anomalous signals generated from direct interaction with the APDs. The VFE (Very Front-End) card will be equipped with two new ASICs: a fast trans-impedance amplifier named CATIA as well as a data conversion and compression ASIC named LiTE-DTU. The VFE will interface with the radiation tolerant LpGBT transceiver and the VTRx+ optical board, while trigger primitive generation will be moved off-detector to FPGA-based processors. The CATIA ASIC has a single input and two differential outputs with different gains in order to have better resolution for low energy signals. CATIA is designed in commercial CMOS 130 nm technology and can be controlled via an I2C interface. The LiTE-DTU ASIC embeds two 12-bit 160 MS/s ADCs, a sample selection logic, a lossless compression digital logic, and a 1.28 Gb/s serializer that will directly interface with the LpGBT e-links. LiTE-DTU is designed in commercial CMOS 65 nm technology. It embeds a PLL for the generation of the low jitter 1.28 GHz clock required by the ADCs and the serializer. Both ASICs have been extensively tested in lab and beam tests. This new system has been verified to fulfill the requirements of the experiment in terms of performance and radiation tolerance. The ASICs are now in the pre-production phase.
In this paper we present the partial wave unitarity bound in the parameter space of dimension-5 and dimension-6 effective operators that arise in a compositeness scenario. These are routinely used in ...experimental searches at the LHC to constraint contact and gauge interactions between ordinary Standard Model fermions and excited (composite) states of mass M. After deducing the unitarity bound for the production process of a composite neutrino, we implement such bound and compare it with the recent experimental exclusion curves for Run 2, the High-Luminosity and High-Energy configurations of the LHC. Our results also applies to the searches where a generic single excited state is produced via contact interactions. We find that the unitarity bound, so far overlooked, is quite compelling and significant portions of the parameter space (M,Λ) become excluded in addition to the standard request M≥Λ.
Pixelated silicon detectors are state-of-the-art technology to achieve precise tracking and vertexing at collider experiments, designed to accurately measure the hit position of incoming particles in ...high rate and radiation environments. The detector requirements become extremely demanding for operation at the High-Luminosity LHC, where up to 200 interactions will overlap in the same bunch crossing on top of the process of interest. Additionally, fluences up to 2.3 × 1016cm−2 1MeV neutron equivalent at 3.0cm distance from the beam are expected for an integrated luminosity of 3000fb−1. In the last decades, the pixel pitch has constantly been reduced to cope with the experiments’ needs of achieving higher position resolution and maintaining low pixel occupancy per channel. The spatial resolution improves with a decreased pixel size but it degrades with radiation damage. Therefore, prototype sensor modules for the upgrade of the experiments at the HL-LHC need to be tested after being irradiated. This paper describes position resolution measurements on planar prototype sensors with 100 × 25µm2 pixels for the CMS Phase-2 Upgrade. It reviews the dependence of the position resolution on the relative inclination angle between the incoming particle trajectory and the sensor, the charge threshold applied by the readout chip and the bias voltage. A precision setup with three parallel planes of sensors has been used to investigate the performance of sensors irradiated to fluences up to ϕeq=3.6×1015 cm−2. The measurements were performed with a 5GeV electron beam. A spatial resolution of 3.2±0.1µm is found for non-irradiated sensors, at the optimal angle for charge sharing. The resolution is 5.0±0.2µm for a proton-irradiated sensor at ϕeq=2.1×1015 cm−2 and a neutron-irradiated sensor at ϕeq=3.6×1015 cm−2. The extrapolated resolution to infinite beam momentum, where the contribution of multiple scattering can be neglected, has also been evaluated.
The Forward Physics Facility (FPF) is a proposal to create a cavern with the space and infrastructure to support a suite of far-forward experiments at the Large Hadron Collider during the High ...Luminosity era. Located along the beam collision axis and shielded from the interaction point by at least 100 m of concrete and rock, the FPF will house experiments that will detect particles outside the acceptance of the existing large LHC experiments and will observe rare and exotic processes in an extremely low-background environment. In this work, we summarize the current status of plans for the FPF, including recent progress in civil engineering in identifying promising sites for the FPF and the experiments currently envisioned to realize the FPF’s physics potential. We then review the many Standard Model and new physics topics that will be advanced by the FPF, including searches for long-lived particles, probes of dark matter and dark sectors, high-statistics studies of TeV neutrinos of all three flavors, aspects of perturbative and non-perturbative QCD, and high-energy astroparticle physics.
The Large Hadron–Electron Collider at the HL-LHC Aksakal, H; Alekhin, S; Allport, P P ...
Journal of physics. G, Nuclear and particle physics,
11/2021, Letnik:
48, Številka:
11
Journal Article
This Letter describes a search for Higgs boson pair production using the combined results from four final states: bbγγ, bbττ, bbbb, and bbVV, where V represents a W or Z boson. The search is ...performed using data collected in 2016 by the CMS experiment from LHC proton-proton collisions at √s = 13 TeV, corresponding to an integrated luminosity of 35.9 fb−1. Limits are set on the Higgs boson pair production cross section. A 95% confidence level observed (expected) upper limit on the nonresonant production cross section is set at 22.2 (12.8) times the standard model value. A search for narrow resonances decaying to Higgs boson pairs is also performed in the mass range 250–3000 GeV. No evidence for a signal is observed, and upper limits are set on the resonance production cross section.
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