1,708 research outputs found
Search for the Exclusive W Boson Hadronic Decays W± → π±γ, W± → K±γ and W± → ρ±γ with the ATLAS Detector
No full textA search for the exclusive hadronic decays W^{±}→π^{±}γ, W^{±}→K^{±}γ, and W^{±}→ρ^{±}γ is performed using up to 140 fb^{-1} of proton-proton collisions recorded with the ATLAS detector at a center-of-mass energy of sqrt[s]=13 TeV. If observed, these rare processes would provide a unique test bench for the quantum chromodynamics factorization formalism used to calculate cross sections at colliders. Additionally, at future colliders, these decays could offer a new way to measure the W boson mass through fully reconstructed decay products. The search results in the most stringent upper limits to date on the branching fractions B(W^{±}→π^{±}γ)<1.9×10^{-6}, B(W^{±}→K^{±}γ)<1.7×10^{-6}, B(W^{±}→ρ^{±}γ)<5.2×10^{-6} at 95% confidence level
Search for the Exclusive W Boson Hadronic Decays W±→π±γ , W±→K±γ and W±→ρ±γ with the ATLAS Detector
No full textA search for the exclusive hadronic decays W± → π±γ, W± → K±γ, and W± → ρ±γ is performed using
up to 140 fb−1 of proton-proton collisions recorded with the ATLAS detector at a center-of-mass energy of √s = 13 TeV. If observed, these rare processes would provide a unique test bench for the quantum
chromodynamics factorization formalism used to calculate cross sections at colliders. Additionally, at
future colliders, these decays could offer a new way to measure the W boson mass through fully
reconstructed decay products. The search results in the most stringent upper limits to date on the branching
fractions B(W± → π±γ) < 1.9 × 10−6, B(W± → K±γ) < 1.7 × 10−6, B(W± → ρ±γ) < 5.2 × 10−6 at
95% confidence level
Search for triboson production in collisions at TeV with the ATLAS detector
No full textSee paper for full list of authors - Comments: 39 pages in total, author list starting page 23, 5 figures, 7 tables, submitted to European Physics Journal C, All figures including auxiliary figures are available at https://atlas.web.cern.ch/Atlas/GROUPS/PHYSICS/PAPERS/STDM-2015-07/International audienceThis paper reports a search for triboson production in two decay channels ( and with ) in proton-proton collision data corresponding to an integrated luminosity of 20.3 fb at a centre-of-mass energy of 8 TeV with the ATLAS detector at the Large Hadron Collider. Events with exactly three charged leptons, or two leptons with the same electric charge in association with two jets, are selected. The total number of events observed in data is consistent with the Standard Model (SM) predictions. The observed 95 % confidence level upper limit on the SM production cross section is found to be 730 fb with an expected limit of 560 fb in the absence of SM production. Limits are also set on anomalous quartic gauge couplings
Search for the exclusive boson hadronic decays , and with the ATLAS detector
No full textA search for the exclusive hadronic decays , and is performed using up to of proton-proton collisions recorded with the ATLAS detector at a center-of-mass energy of . These rare processes provide a test bench for the quantum chromodynamics factorization formalism used to calculate cross sections at colliders, as well as a probe of boson coupling to quarks and a new way to measure the boson mass through fully reconstructed decay products. The search results in the most stringent upper limit to date on the branching fractions \mathcal{B}(W^{\pm}\to \pi^{\pm}\gamma) W±→π±γ, W±→K±γ, and W±→ρ±γ is performed using up to 140 fb-1 of proton-proton collisions recorded with the ATLAS detector at a center-of-mass energy of s=13 TeV. If observed, these rare processes would provide a unique test bench for the quantum chromodynamics factorization formalism used to calculate cross sections at colliders. Additionally, at future colliders, these decays could offer a new way to measure the W boson mass through fully reconstructed decay products. The search results in the most stringent upper limits to date on the branching fractions B(W±→π±γ)<1.9×10-6, B(W±→K±γ)<1.7×10-6, B(W±→ρ±γ)<5.2×10-6 at 95% confidence level.A search for the exclusive hadronic decays W^{\pm}\to \pi^{\pm}\gammaW^{\pm}\to K^{\pm}\gammaW^{\pm}\to \rho^{\pm}\gamma140\, \text{fb}^{-1}\sqrt{s}=13\,\text{TeV}WW\mathcal{B}(W^{\pm}\to \pi^{\pm}\gamma) < 1.9\times10^{-6}\mathcal{B}(W^{\pm}\to K^{\pm}\gamma) < 1.7\times10^{-6}\mathcal{B}(W^{\pm}\to \rho^{\pm}\gamma) < 5.2\times10^{-6}$ at 95% confidence level
Measurement of vector-boson scattering and limits on anomalous quartic gauge couplings with the ATLAS detector
No full textSee paper for full list of authors - 49 pages in total, author list starting page 33, 13 figures, 12 tables, submitted to Physical Review D, all figures including auxiliary figures are available at https://atlas.web.cern.ch/Atlas/GROUPS/PHYSICS/PAPERS/STDM-2014-05/International audienceThis paper presents the extended results of measurements of W±W±jj production and limits on anomalous quartic gauge couplings using 20.3 fb−1 of proton-proton collision data at s√=8 TeV recorded by the ATLAS detector at the Large Hadron Collider. Events with two leptons (e or μ) with the same electric charge and at least two jets are analyzed. Production cross-sections are determined in two fiducial regions, with different sensitivities to the electroweak and strong production mechanisms. An additional fiducial region, particularly sensitive to anomalous quartic gauge coupling parameters α4 and α5, is introduced, which allows more stringent limits on these parameters compared to the previous ATLAS measurement
Measurements of W + W - production in decay topologies inspired by searches for electroweak supersymmetry
No full textAbstract This paper presents a measurement of fiducial and differential cross-sections for W + W - production in proton–proton collisions at s = 13 TeV with the ATLAS experiment at the Large Hadron Collider using a dataset corresponding to an integrated luminosity of 139 fb - 1 . Events with exactly one electron, one muon and no hadronic jets are studied. The fiducial region in which the measurements are performed is inspired by searches for the electroweak production of supersymmetric charginos decaying to two-lepton final states. The selected events have moderate values of missing transverse momentum and the ‘stransverse mass’ variable m T2 , which is widely used in searches for supersymmetry at the LHC. The ranges of these variables are chosen so that the acceptance is enhanced for direct W + W - production and suppressed for production via top quarks, which is treated as a background. The fiducial cross-section and particle-level differential cross-sections for six variables are measured and compared with two theoretical SM predictions from perturbative QCD calculations
Measurement of the production cross section in collisions at a centre-of-mass energy of = 13 TeV with the ATLAS experiment
No full textSee paper for full list of authors - 37 pages in total, author list starting page 21, 8 figures, 8 tables, submitted to Phys. Lett. B. All figures including auxiliary figures are available at http://atlas.web.cern.ch/Atlas/GROUPS/PHYSICS/PAPERS/STDM-2015-20/International audienceThe production of opposite-charge -boson pairs in proton-proton collisions at = 13 TeV is measured using data corresponding to 3.16 fb of integrated luminosity collected by the ATLAS detector at the CERN Large Hadron Collider in 2015. Candidate -boson pairs are selected by identifying their leptonic decays into an electron, a muon and neutrinos. Events with reconstructed jets are not included in the candidate event sample. The cross-section measurement is performed in a fiducial phase space close to the experimental acceptance and is compared to theoretical predictions. Agreement is found between the measurement and the most accurate calculations available
Test of the universality of and lepton couplings in -boson decays from events with the ATLAS detector
No full textThe Standard Model of particle physics encapsulates our current best
understanding of physics at the smallest scales. A fundamental axiom of this
theory is the universality of the couplings of the different generations of
leptons to the electroweak gauge bosons. The measurement of the ratio of the
rate of decay of bosons to -leptons and muons, , constitutes an important test of this
axiom. A measurement of this quantity with a novel technique using di-leptonic
events is presented based on 139 fb of data recorded with
the ATLAS detector in proton--proton collisions at TeV. Muons
originating from bosons and those originating from an intermediate
-lepton are distinguished using the lifetime of the -lepton,
through the muon transverse impact parameter, and differences in the muon
transverse momentum spectra. The value of is found to be and is in agreement with the
hypothesis of universal lepton couplings as postulated in the Standard Model.
This is the most precise measurement of this ratio, and the only such
measurement from the Large Hadron Collider, to date.Comment: 33 pages in total, author list starting page 17, 4 figures, 2 tables,
submitted to Nature Physics. All figures including auxiliary figures are
available at
http://atlas.web.cern.ch/Atlas/GROUPS/PHYSICS/PAPERS/TOPQ-2018-2
High throughput screens yield small molecule inhibitors of <i>Leishmania</i> CRK3:CYC6 cyclin-dependent kinase
No full text<p><b>Background:</b> <i>Leishmania</i> species are parasitic protozoa that have a tightly controlled cell cycle, regulated by cyclin-dependent kinases (CDKs). Cdc2-related kinase 3 (CRK3), an essential CDK in <i>Leishmania</i> and functional orthologue of human CDK1, can form an active protein kinase complex with Leishmania cyclins CYCA and CYC6. Here we describe the identification and synthesis of specific small molecule inhibitors of bacterially expressed <i>Leishmania</i> CRK3: CYC6 using a high throughput screening assay and iterative chemistry. We also describe the biological activity of the molecules against <i>Leishmania</i> parasites.</p>
<p><b>Methodology/Principal Findings:</b> In order to obtain an active <i>Leishmania</i> CRK3: CYC6 protein kinase complex, we developed a co-expression and co-purification system for <i>Leishmania</i> CRK3 and CYC6 proteins. This active enzyme was used in a high throughput screening (HTS) platform, utilising an IMAP fluorescence polarisation assay. We carried out two chemical library screens and identified specific inhibitors of CRK3: CYC6 that were inactive against the human cyclin-dependent kinase CDK2: CycA. Subsequently, the best inhibitors were tested against 11 other mammalian protein kinases. Twelve of the most potent hits had an azapurine core with structure activity relationship (SAR) analysis identifying the functional groups on the 2 and 9 positions as essential for CRK3: CYC6 inhibition and specificity against CDK2: CycA. Iterative chemistry allowed synthesis of a number of azapurine derivatives with one, compound 17, demonstrating anti-parasitic activity against both promastigote and amastigote forms of <i>L. major</i>. Following the second HTS, 11 compounds with a thiazole core (active towards CRK3: CYC6 and inactive against CDK2: CycA) were tested. Ten of these hits demonstrated anti-parasitic activity against promastigote <i>L. major</i>.</p>
<p><b>Conclusions/Significance:</b> The pharmacophores identified from the high throughput screens, and the derivatives synthesised, selectively target the parasite enzyme and represent compounds for future hit-to-lead synthesis programs to develop therapeutics against <i>Leishmania</i> species. Challenges remain in identifying specific CDK inhibitors with both target selectivity and potency against the parasite.</p>
Measurement of the production of a W boson in association with a charmed hadron in pp collisions at p s=13 TeV with the ATLAS detector
No full textThe production of a W boson in association with a single charm quark is studied using 140 fb - 1 of s = 13 TeV proton-proton collision data collected with the ATLAS detector at the Large Hadron Collider. The charm quark is tagged by the presence of a charmed hadron reconstructed with a secondary-vertex fit. The W boson is reconstructed from the decay to either an electron or a muon and the missing transverse momentum present in the event. The charmed mesons reconstructed are D + → K - π + π + and D * + → D 0 π + → ( K - π + ) π + and the charge conjugate decays in the fiducial regions where p T ( e , μ ) > 30 GeV , | η ( e , μ ) | 8 GeV , and | η ( D ( * ) ) | < 2.2 . The integrated and normalized differential cross sections as a function of the pseudorapidity of the lepton from the W boson decay, and of the transverse momentum of the charmed hadron, are extracted from the data using a profile likelihood fit. The measured total fiducial cross sections are σ fid OS - SS ( W - + D + ) = 50.2 ± 0.2 ( stat ) - 2.3 + 2.4 ( syst ) pb , σ fid OS - SS ( W + + D - ) = 48.5 ± 0.2 ( stat ) - 2.2 + 2.3 ( syst ) pb , σ fid OS - SS ( W - + D * + ) = 51.1 ± 0.4 ( stat ) - 1.8 + 1.9 ( syst ) pb , and σ fid OS - SS ( W + + D * - ) = 50.0 ± 0.4 ( stat ) - 1.8 + 1.9 ( syst ) pb . Results are compared with the predictions of next-to-leading-order quantum chromodynamics calculations performed using state-of-the-art parton distribution functions. Additionally, the ratio of charm to anticharm production cross sections is studied to probe the s - s ̄ quark asymmetry. The ratio is found to be R c ± = 0.971 ± 0.006 ( stat ) ± 0.011 ( syst ) . The ratio and cross-section measurements are consistent with the predictions obtained with parton distribution function sets that have a symmetric s - s ̄ sea, indicating that any s - s ̄ asymmetry in the Bjorken- x region relevant for this measurement is small
- …
