118 research outputs found
Elliptic flow of charged particles at midrapidity relative to the spectator plane in PbâPb and XeâXe collisions
Measurements of the elliptic flow coefficient relative to the collision plane defined by the spectator neutrons v2{ SP} in collisions of Pb ions at center-of-mass energy per nucleonânucleon pair â 2.76 TeV and Xe ions at â sNN = sNN =5.44 TeV are reported. The results are presented for charged particles produced at midrapidity as a function of centrality and transverse momentum for the 5â70% and 0.2â6 GeV/c ranges, respectively. The ratio between v2{ SP} and the elliptic flow coefficient relative to the participant plane v2{4}, estimated using four-particle correlations, deviates by up to 20% from unity depending on centrality. This observation differs strongly from the magnitude of the corresponding eccentricity ratios predicted by the TRENTo and the elliptic power models of initial state fluctuations that are tuned to describe the participant plane anisotropies. The differences can be interpreted as a decorrelation of the neutron spectator plane and the reaction plane because of fragmentation of the remnants from the colliding nuclei, which points to an incompleteness of current models describing the initial state fluctuations. A significant transverse momentum dependence of the ratio v2{ SP}/v2{4} is observed in all but the most central collisions, which may help to understand whether momentum anisotropies at low and intermediate transverse momentum have a common origin in initial state f luctuations. The ratios of v2{ SP} and v2{4} to the corresponding initial state eccentricities for XeâXe and PbâPb collisions at similar initial entropy density show a difference of (7.0 ±0.9)%with an additional variation of +1.8% when including RHIC data in the TRENTo parameter extraction. These observations provide new experimental constraints for viscous effects in the hydrodynamic modeling of the expanding quarkâgluon plasma produced in heavy-ion collisions at the LHC
First measurement of Ωc0 production in pp collisions at s=13 TeV
The inclusive production of the charmâstrange baryon 0 c is measured for the first time via its hadronic â decay into âÏ+ at midrapidity (|y| <0.5) in protonâproton (pp) collisions at the centre-of-mass energy s =13 TeV with the ALICE detector at the LHC. The transverse momentum (pT) differential cross section multiplied by the branching ratio is presented in the interval 2 < pT < 12 GeV/c. The pT dependence of the 0 c-baryon production relative to the prompt D0-meson and to the prompt 0 c-baryon production is compared to various models that take different hadronisation mechanisms into consideration. In the measured pT interval, the ratio of the pT-integrated cross sections of 0 c and prompt + c baryons multiplied by the âÏ+ branching ratio is found to be larger by a factor of about 20 with a significance of about 4Ï when compared to e+eâ collisions
Orbital lesion (pseudotumor and dacryoadenitis) is a manifestation of systemic sarcoidosis
E.A. Burylova, L.A. Mamaeva, A.S. Berdnikova, O.K. Fedorova
Ural Scientific Research Institute of Phtysiopulmonology â Branch of the National Medical Research Center of Phtysiopulmonology, Yekaterinburg, Russian Federation
Abstract
Ocular manifestations of systemic sarcoidosis may emerge at any disease stage. Ocular sarcoidosis is typically characterized by uveitic presentations that predominantly involve the choroid of anterior eye segment. However, orbital pseudotumor, dacryoadenitis, and other rare presentations (optic neuritis, dacryocystitis etc.) also occur in sarcoidosis. Threatened vision loss and poor quality of life are the reasons to prescribe systemic steroids in generalized sarcoidosis. Chest CT is required to identify respiratory diseases when sarcoidosis manifests as uveitis or granulomatous orbital inflammation. Multidisciplinary diagnostic and treatment approach to suspected sarcoidosis provides timely verified diagnosis and management strategy. This paper addresses case report of systemic sarcoidosis in a 34-year-old man. The initial manifestation was vision loss and left orbital pseudotumor. The enlarged subclavian lymph node and its biopsy were suspicious of granulomatous inflammation. Chest CT identified disseminated pulmonary lesions and intrathoracic lymphadenopathy that are typical of sarcoidosis. The results of multidisciplinary examina tions verified systemic sarcoidosis. Systemic steroids resulted in clinical and radiological improvement and medicinal regression of the disease.
Keywords: sarcoidosis, orbital pseudotumor, dacryoadenitis, adenopathy, computed tomography, multidisciplinary approach.
For citation: Burylova E.A., Mamaeva L.A., Berdnikova A.S., Fedorova O.K. Orbital lesion (pseudotumor and dacryoadenitis) is a manifestation of systemic sarcoidosis. Russian Journal of Clinical Ophthalmology. 2021;21(1):40â44. DOI: 10.32364/2311-7729-2021-21-1-40-44.
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Regio- and stereoselective [2+2] photocycloaddition in Ba2+ templated supramolecular dimers of styryl-derivatized aza-heterocycles
The regio- and stereoselective [2+2] photocycloaddition of 15-crown-5-containing styrylheterocycles resulting in formation of only one cyclobutane isomer out of eleven possible is described. It was shown that the cycloaddition takes place solely in the case of the supramolecular preorganization of the reactive molecules provided by both ÏâÏ stacking interaction of the heterocyclic fragments and sandwich-type coordination of the crown ether residues by the barium cation. The results point out the importance of the supramolecular approach for the synthesis of cyclobutane derivatives with desired structure and conformation. © 2016 Elsevier Lt
Regio- and stereoselective [2+2] photocycloaddition in Ba2+ templated supramolecular dimers of styryl-derivatized aza-heterocycles
The regio- and stereoselective [2+2] photocycloaddition of 15-crown-5-containing styrylheterocycles resulting in formation of only one cyclobutane isomer out of eleven possible is described. It was shown that the cycloaddition takes place solely in the case of the supramolecular preorganization of the reactive molecules provided by both ÏâÏ stacking interaction of the heterocyclic fragments and sandwich-type coordination of the crown ether residues by the barium cation. The results point out the importance of the supramolecular approach for the synthesis of cyclobutane derivatives with desired structure and conformation. © 2016 Elsevier Lt
First measurement of <math><msubsup><mi mathvariant="normal">Î</mi><mrow><mi>c</mi></mrow><mo>+</mo></msubsup></math> production down to <math><mrow><msub><mi>p</mi><mi>T</mi></msub><mo>=</mo><mn>0</mn></mrow></math> in <math><mrow><mi>p</mi><mi>p</mi></mrow></math> and <math><mi>p</mi></math>-Pb collisions at <math><mrow><msqrt><msub><mi>s</mi><mrow><mi>N</mi><mi>N</mi></mrow></msub></msqrt><mo>=</mo><mn>5.02</mn></mrow></math> TeV
International audienceThe production of prompt Îc+ baryons has been measured at midrapidity in the transverse momentum interval 0<pT<1 GeV/c for the first time, in pp and pâPb collisions at a center-of-mass energy per nucleon-nucleon collision sNN=5.02TeV. The measurement was performed in the decay channel Îc+âpKS0 by applying new decay reconstruction techniques using a Kalman-Filter vertexing algorithm and adopting a machine-learning approach for the candidate selection. The pT-integrated Îc+ production cross sections in both collision systems were determined and used along with the measured yields in PbâPb collisions to compute the pT-integrated nuclear modification factors RpPb and RAA of Îc+ baryons, which are compared to model calculations that consider nuclear modification of the parton distribution functions. The Îc+/D0 baryon-to-meson yield ratio is reported for pp and pâPb collisions. Comparisons with models that include modified hadronization processes are presented, and the implications of the results on the understanding of charm hadronization in hadronic collisions are discussed. A significant (3.7Ï) modification of the mean transverse momentum of Îc+ baryons is seen in pâPb collisions with respect to pp collisions, while the pT-integrated Îc+/D0 yield ratio was found to be consistent between the two collision systems within the uncertainties
Azimuthal correlations of heavy-flavor hadron decay electrons with charged particles in pp and pâPb collisions at = 5.02 TeV
International audienceThe azimuthal () correlation distributions between heavy-flavor decay electrons and associated charged particles are measured in pp and pâPb collisions at TeV. Results are reported for electrons with transverse momentum  and pseudorapidity . The associated charged particles are selected with transverse momentum , and relative pseudorapidity separation with the leading electron . The correlation measurements are performed to study and characterize the fragmentation and hadronization of heavy quarks. The correlation structures are fitted with a constant and two von Mises functions to obtain the baseline and the near- and away-side peaks, respectively. The results from pâPb collisions are compared with those from pp collisions to study the effects of cold nuclear matter. In the measured trigger electron and associated particle kinematic regions, the two collision systems give consistent results. The distribution and the peak observables in pp and pâPb collisions are compared with calculations from various Monte Carlo event generators
Measurements of groomed-jet substructure of charm jets tagged by mesons in protonâproton collisions at = 13 TeV
Understanding the role of parton mass and Casimir colour factors in the quantum chromodynamics parton shower represents an important step in characterising the emission properties of heavy quarks. Recent experimental advances in jet substructure techniques have provided the opportunity to isolate and characterise gluon emissions from heavy quarks. In this work, the first direct experimental constraint on the charm-quark splitting function is presented, obtained via the measurement of the groomed shared momentum fraction of the first splitting in charm jets, tagged by a reconstructed meson. The measurement is made in proton-proton collisions at TeV, in the low jet transverse-momentum interval of GeV/ where the emission properties are sensitive to parton mass effects. In addition, the opening angle of the first perturbative emission of the charm quark, as well as the number of perturbative emissions it undergoes, are reported. Comparisons to measurements of an inclusive-jet sample show a steeper splitting function for charm quarks compared to gluons and light quarks. Charm quarks also undergo fewer perturbative emissions in the parton shower, with a reduced probability of large-angle emissions.Understanding the role of parton mass and Casimir colour factors in the quantum chromodynamics parton shower represents an important step in characterising the emission properties of heavy quarks. Recent experimental advances in jet substructure techniques have provided the opportunity to isolate and characterise gluon emissions from heavy quarks. In this work, the first direct experimental constraint on the charm-quark splitting function is presented, obtained via the measurement of the groomed shared momentum fraction of the first splitting in charm jets, tagged by a reconstructed meson. The measurement is made in proton--proton collisions at = 13 TeV, in the low jet transverse-momentum interval of GeV/ where the emission properties are sensitive to parton mass effects. In addition, the opening angle of the first perturbative emission of the charm quark, as well as the number of perturbative emissions it undergoes, are reported. Comparisons to measurements of an inclusive-jet sample show a steeper splitting function for charm quarks compared to gluons and light quarks. Charm quarks also undergo fewer perturbative emissions in the parton shower, with a reduced probability of large-angle emissions
Accessing the strong interaction between Î baryons and charged kaons with the femtoscopy technique at the LHC
The interaction between Î baryons and kaons/antikaons is a crucial ingredient for the strangeness S=0 and S=â2 sector of the mesonâbaryon interaction at low energies. In particular, the ÎK⟠might help in understanding the origin of states such as the Î(1620), whose nature and properties are still under debate. Experimental data on ÎâK and ÎâK⟠systems are scarce, leading to large uncertainties and tension between the available theoretical predictions constrained by such data. In this Letter we present the measurements of ÎâKâ+ÎâŸâKâ and ÎâKââÎâŸâK+ correlations obtained in the high-multiplicity triggered data sample in pp collisions at s=13 TeV recorded by ALICE at the LHC. The correlation function for both pairs is modeled using the LednickĂœâLyuboshits analytical formula and the corresponding scattering parameters are extracted. The ÎâKââÎâŸâK+ correlations show the presence of several structures at relative momenta kâ above 200 MeV/c, compatible with the Ω baryon, the Î(1690), and Î(1820) resonances decaying into ÎâKâ pairs. The low kâ region in the ÎâKââÎâŸâK+ also exhibits the presence of the Î(1620) state, expected to strongly couple to the measured pair. The presented data allow to access the ÎK+ and ÎKâ strong interaction with an unprecedented precision and deliver the first experimental observation of the Î(1620) decaying into ÎKâ
Production of pions, kaons, and protons as a function of the relative transverse activity classifier in pp collisions at = 13 TeV
International audienceThe production of Ï, K, and is measured in pp collisions at = 13 TeV in different topological regions of the events. Particle transverse momentum (p) spectra are measured in the âtowardâ, âtransverseâ, and âawayâ angular regions defined with respect to the direction of the leading particle in the event. While the toward and away regions contain the fragmentation products of the near-side and away-side jets, respectively, the transverse region is dominated by particles from the Underlying Event (UE). The relative transverse activity classifier, Râ=âN/â©NâȘ, is used to group events according to their UE activity, where N is the measured charged-particle multiplicity per event in the transverse region and â©NâȘ is the mean value over all the analysed events. The first measurements of identified particle p spectra as a function of R in the three topological regions are reported. It is found that the yield of high transverse momentum particles relative to the R-integrated measurement decreases with increasing R in both the toward and the away regions, indicating that the softer UE dominates particle production as R increases and validating that R can be used to control the magnitude of the UE. Conversely, the spectral shapes in the transverse region harden significantly with increasing R. This hardening follows a mass ordering, being more significant for heavier particles. Finally, it is observed that the p-differential particle ratios \left(\textrm{p}+\overline{\textrm{p}}\right)/\left({\uppi}^{+}+{\uppi}^{-}\right) and (K + K)/(Ï + Ï) in the low UE limit (R â 0) approach expectations from Monte Carlo generators such as PYTHIA 8 with Monash 2013 tune and EPOS LHC, where the jet-fragmentation models have been tuned to reproduce ee results.[graphic not available: see fulltext
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