Quark-lepton compositeness is a well-known beyond the Standard Model (SM) scenario with heavy exotic particles like leptoquarks (LQs) and leptogluons (LGs) etc. These particles can couple to leptons ...and jets simultaneously. In this letter, we use the recent CMS scalar LQ search data in the eejj and eej channels to probe this scenario. We recast the data in terms of a color octet partner of the SM electron (or a first generation spin-1/2 LG) that couples to an electron and a gluon via a dimension five operator suppressed by the quark–lepton compositeness scale (Λ). By combining different production processes of the color octet electron (e8) at the LHC, we use the CMS 8 TeV data to obtain a simultaneous bound on Λ and the mass of the e8 (Me8). We also study the reach of the 13 TeV LHC to discover the e8 and interpret the required luminosity in terms of Me8 and Λ.
The steadily increasing luminosity of the LHC requires an upgrade with high-rate and high-resolution detector technology for the inner end cap of the ATLAS muon spectrometer: the New Small Wheels ...(NSW). In order to achieve the goal of precision tracking at a hit rate of about 15 kHz/cm2 at the inner radius of the NSW, large area Micromegas quadruplets with 100µm spatial resolution per plane have been produced. IRFU, from the CEA research center of Saclay, is responsible for the production and validation of LM1 Micromegas modules. The construction, production, qualification and validation of the largest Micromegas detectors ever built are reported here. Performance results under cosmic muon characterization will also be discussed.
Results on the production of 4He and He ¯ 4 nuclei in Pb–Pb collisions at s NN = 2.76 TeV in the rapidity range | y | < 1 , using the ALICE detector, are presented in this paper. The rapidity ...densities corresponding to 0–10% central events are found to be d N / d y He 4 = ( 0.8 ± 0.4 ( stat ) ± 0.3 ( syst ) ) × 10 - 6 and d N / d y He ¯ 4 = ( 1.1 ± 0.4 ( stat ) ± 0.2 ( syst ) ) × 10 - 6 , respectively. This is in agreement with the statistical thermal model expectation assuming the same chemical freeze-out temperature ( T chem = 156 MeV ) as for light hadrons. The measured ratio of He ¯ 4 / 4 He is 1.4 ± 0.8 ( stat ) ± 0.5 ( syst ) .
The large increase of pileup is one of the main experimental challenges for the HL-LHC physics program. A powerful new way to address this challenge is to exploit the time spread of the interactions ...to distinguish between collisions occurring very close in space but well separated in time. A High-Granularity Timing Detector, based on low gain avalanche detector technology, is proposed for the ATLAS Phase-II upgrade. Covering the pseudorapidity region between 2.4 and 4.0, with a timing resolution of 30 ps for minimum-ionizing particles, this device will significantly improve the performance in the forward region. High-precision timing greatly improves the track-to-vertex association, leading to a performance similar to that in the central region for the reconstruction of both jets and leptons, as well as for the tagging of heavy-flavor jets. These improvements in object reconstruction performance translate into important sensitivity gains and enhance the reach of the HL-LHC physics program. In addition, the High-Granularity Timing Detector offers unique capabilities for the online and offline luminosity determination.
•During the HL-LHC program high pileup impacts the reconstruction of physics objects.•A forward timing detector can improve the performance of the ATLAS detector.•LGAD sensors of size 1.3 × 1.3 mm2 can reach a timing resolution of 30 ps.•Forward highly granular detector can be used to measure the luminosity.
Charge collection in irradiated HV-CMOS detectors Hiti, B.; Affolder, A.; Arndt, K. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
04/2019, Letnik:
924, Številka:
C
Journal Article
Recenzirano
Odprti dostop
Active silicon detectors built on p-type substrate are a promising technological solution for large area silicon trackers such as those at the High Luminosity LHC, but the radiation hardness of this ...novel approach has to be evaluated. Active n-in-p strip detector prototypes CHESS2 for ATLAS with different substrate resistivities in the range of 20–1000 Ωcm were irradiated with neutrons and protons up to a fluence of 2×1015neqcm−2 and 3.6×1015neqcm−2. Charge collection in passive test structures on the chip was evaluated using Edge-TCT and minimum ionising electrons from 90Sr. Results were used to assess radiation hardness of the detector in the given fluence range and to determine parameters of initial acceptor removal in different substrates.
•Irradiated samples of different initial resistivity between 20 and a few 1000 Ω cm.•Characterisation with edge transient current technique and 90Sr beta electrons.•Sensitive region increases after irradiation due to acceptor removal.•Parameters of acceptor removal estimated for neutron irradiation.•After proton irradiation larger sensitive region than after neutron irradiation.
Ferrochelatase (FeCh) is an essential enzyme catalyzing the synthesis of heme. Interestingly, in cyanobacteria, algae, and plants, FeCh possesses a conserved transmembrane chlorophyll a/b binding ...(CAB) domain that resembles the first and the third helix of light-harvesting complexes, including a chlorophyll-binding motif. Whether the FeCh CAB domain also binds chlorophyll is unknown. Here, using biochemical and radiolabeled precursor experiments, we found that partially inhibited activity of FeCh in the cyanobacterium Synechocystis PCC 6803 leads to overproduction of chlorophyll molecules that accumulate in the thylakoid membrane and, together with carotenoids, bind to FeCh. We observed that pigments bound to purified FeCh are organized in an energy-dissipative conformation and further show that FeCh can exist in vivo as a monomer or a dimer depending on its own activity. However, pigmented FeCh was purified exclusively as a dimer. Separately expressed and purified FeCH CAB domain contained a pigment composition similar to that of full-length FeCh and retained its quenching properties. Phylogenetic analysis suggested that the CAB domain was acquired by a fusion between FeCh and a single-helix, high light-inducible protein early in the evolution of cyanobacteria. Following this fusion, the FeCh CAB domain with a functional chlorophyll-binding motif was retained in all currently known cyanobacterial genomes except for a single lineage of endosymbiotic cyanobacteria. Our findings indicate that FeCh from Synechocystis exists mostly as a pigment-free monomer in cells but can dimerize, in which case its CAB domain creates a functional pigment-binding segment organized in an energy-dissipating configuration.
The LHC Injectors Upgrade (LIU) program included new fast beam wire scanners (BWS) to meet the requirements of the higher brightness and intensity High Luminosity LHC (HL-LHC) beams. Seventeen LIU ...BWS have been installed during the LHC second long shutdown (LS2) and they are currently used in the daily operations of the LHC injectors. After giving an overview of the LIU project and the general beam instrumentation upgrades associated with it, this paper presents a short review of the mechanical design and layout of the LIU BWS, the electronics involved, and then focuses on the first results obtained during their commissioning.
In this work we report on the production of charged pions, kaons, and (anti) protons in pp and Pb–Pb collisions at sNN=2.76TeV for 3<pT<20GeV/c. The evolution of the nuclear modification factor, RAA, ...with collision centrality and transverse momentum is discussed.
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