A
bstract
The recent discovery, by the LHCb collaboration, of the Ξ
cc
+ +
doubly charmed baryon, has renewed interest in the spectroscopy of doubly heavy hadrons. Experimentally, however, searches ...for such states appear highly challenging. The reconstructed final states tend to involve multiple heavy flavoured (beauty or charm) hadrons, so the yield for any exclusive decay mode will be suppressed to unobservably low levels by the product of several branching fractions, each of which is typically 10
−3
–10
−2
. Noting that decays of double beauty hadrons are the only possible source of
B
c
−
mesons that are displaced from the primary vertices of proton-proton collisions at the LHC, a more promising inclusive search strategy is proposed.
We observed a syndrome of intermittent fevers, early-onset lacunar strokes and other neurovascular manifestations, livedoid rash, hepatosplenomegaly, and systemic vasculopathy in three unrelated ...patients. We suspected a genetic cause because the disorder presented in early childhood.
We performed whole-exome sequencing in the initial three patients and their unaffected parents and candidate-gene sequencing in three patients with a similar phenotype, as well as two young siblings with polyarteritis nodosa and one patient with small-vessel vasculitis. Enzyme assays, immunoblotting, immunohistochemical testing, flow cytometry, and cytokine profiling were performed on samples from the patients. To study protein function, we used morpholino-mediated knockdowns in zebrafish and short hairpin RNA knockdowns in U937 cells cultured with human dermal endothelial cells.
All nine patients carried recessively inherited mutations in CECR1 (cat eye syndrome chromosome region, candidate 1), encoding adenosine deaminase 2 (ADA2), that were predicted to be deleterious; these mutations were rare or absent in healthy controls. Six patients were compound heterozygous for eight CECR1 mutations, whereas the three patients with polyarteritis nodosa or small-vessel vasculitis were homozygous for the p.Gly47Arg mutation. Patients had a marked reduction in the levels of ADA2 and ADA2-specific enzyme activity in the blood. Skin, liver, and brain biopsies revealed vasculopathic changes characterized by compromised endothelial integrity, endothelial cellular activation, and inflammation. Knockdown of a zebrafish ADA2 homologue caused intracranial hemorrhages and neutropenia - phenotypes that were prevented by coinjection with nonmutated (but not with mutated) human CECR1. Monocytes from patients induced damage in cocultured endothelial-cell layers.
Loss-of-function mutations in CECR1 were associated with a spectrum of vascular and inflammatory phenotypes, ranging from early-onset recurrent stroke to systemic vasculopathy or vasculitis. (Funded by the National Institutes of Health Intramural Research Programs and others.).
Using kaon secondary interactions in the material of the Belle detector, we search for both inclusive and exclusive production of the Θ(1540)+. We set an upper limit of 2.5% at the 90% C.L. on the ...ratio of the Θ(1540)+ to Λ(1520) inclusive production cross sections. We also search for the Θ(1540)+ as an intermediate resonance in the charge exchange reaction K+n→pKS0. We set an upper limit of ΓΘ+<0.64 MeV at the 90% C.L. for mΘ+=1.539 MeV/c2. These results are obtained from a 397 fb−1 data sample collected with the Belle detector near the ϒ(4S) resonance, at the KEKB asymmetric energy e+e− collider.
Abstract Weak decays of the vector $${{D} ^*} ^0$$ D ∗ 0 and $${{B} ^{*0}_{({s})}} $$ B ( s ) ∗ 0 mesons to the $${\mu ^+\mu ^-} $$ μ + μ - final state provide novel potential to test the Standard ...Model of particle physics. Such processes have extremely small branching fractions as the vector mesons are able to decay through electromagnetic and (for the $${{D} ^*} ^0$$ D ∗ 0 meson) strong interactions. Nonetheless, the production of copious quantities of these particles in LHC collisions, and the ability to exploit experimental techniques that can suppress background to low levels, provides good potential to reach interesting sensitivity. The possibility to reconstruct these processes as part of the decay chain of $${{{B} ^-}} $$ B - or $${{B} _{c} ^+} $$ B c + mesons appears particularly attractive due to the clean experimental signature of the displaced vertex. Indeed, published LHCb data on $${{{B} ^-}} \rightarrow {{\pi } ^-} {\mu ^+\mu ^-} $$ B - → π - μ + μ - decays already implies a stringent limit on the branching fraction of $${{D} ^{*0}} \rightarrow {\mu ^+\mu ^-} $$ D ∗ 0 → μ + μ - . Estimates are made on the achievable sensitivity to $${{D} ^{*0}} \rightarrow {\mu ^+\mu ^-} $$ D ∗ 0 → μ + μ - and $${{B} ^{*0}_{({s})}} \rightarrow {\mu ^+\mu ^-} $$ B ( s ) ∗ 0 → μ + μ - decays with the LHCb experiment.
Status of the TORCH time-of-flight project Harnew, N.; Bhasin, S.; Blake, T. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
02/2020, Letnik:
952
Journal Article
Recenzirano
Odprti dostop
TORCH is a time-of-flight detector, designed to provide charged π∕K particle identification up to a momentum of 10GeV/c for a 10m flight path. To achieve this level of performance, a time resolution ...of 15 ps per incident particle is required. TORCH uses a plane of quartz of 1 cm thickness as a source of Cherenkov photons, which are then focussed onto square Micro-Channel Plate Photomultipliers (MCP-PMTs) of active area 53 × 53mm2, segmented into 8 × 128 pixels equivalent. A small-scale TORCH demonstrator with a customised MCP-PMT and associated readout electronics has been successfully operated in a 5GeV/c mixed pion/proton beam at the CERN PS facility. Preliminary results indicate that a single-photon resolution better than 100ps can be achieved. The expected performance of a full-scale TORCH detector for the Upgrade II of the LHCb experiment is also discussed.
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