On freeze-out problem in hydro-kinetic approach to A+A collisions

A new method for evaluating spectra and correlations in the hydrodynamic approach is proposed. It is based on an analysis of Boltzmann equations (BE) in terms of probabilities for constituent particles to escape from the interacting system. The conditions of applicability of Cooper-Frye freeze-out prescription are considered within the method. The results are illustrated with a non-relativistic exact solution of BE for expanding spherical fireball as well as with approximate solutions for ellipsoidally expanding ones.Comment: 4 pages including 2 figures, RevTex, stylistic and clarifying corrections are made, submitted to Phys. Rev. Let

Prompt neutrino fluxes from atmospheric charm

We calculate the prompt neutrino flux from atmospheric charm production by cosmic rays, using the dipole picture in a perturbative QCD framework, which incorporates the parton saturation effects present at high energies. We compare our results with the next-to-leading order perturbative QCD result and find that saturation effects are large for neutrino energies above 10^6 GeV, leading to a substantial suppression of the prompt neutrino flux. We comment on the range of prompt neutrino fluxes due to theoretical uncertainties.Comment: 13 pages with 11 figures; expanded discussion, added references, version to be published in Phys. Rev.

Atmospheric Muon Flux at Sea Level, Underground, and Underwater

The vertical sea-level muon spectrum at energies above 1 GeV and the underground/underwater muon intensities at depths up to 18 km w.e. are calculated. The results are particularly collated with a great body of the ground-level, underground, and underwater muon data. In the hadron-cascade calculations, the growth with energy of inelastic cross sections and pion, kaon, and nucleon generation in pion-nucleus collisions are taken into account. For evaluating the prompt muon contribution to the muon flux, we apply two phenomenological approaches to the charm production problem: the recombination quark-parton model and the quark-gluon string model. To solve the muon transport equation at large depths of homogeneous medium, a semi-analytical method is used. The simple fitting formulas describing our numerical results are given. Our analysis shows that, at depths up to 6-7 km w. e., essentially all underground data on the muon intensity correlate with each other and with predicted depth-intensity relation for conventional muons to within 10%. However, the high-energy sea-level data as well as the data at large depths are contradictory and cannot be quantitatively decribed by a single nuclear-cascade model.Comment: 47 pages, REVTeX, 15 EPS figures included; recent experimental data and references added, typos correcte

On inconsistency of experimental data on primary nuclei spectra with sea level muon intensity measurements

For the first time a complete set of the most recent direct data on primary cosmic ray spectra is used as input into calculations of muon flux at sea level in wide energy range $E_\mu=1-3\cdot10^5$ GeV. Computations have been performed with the CORSIKA/QGSJET and CORSIKA/VENUS codes. The comparison of the obtained muon intensity with the data of muon experiments shows, that measurements of primary nuclei spectra conform to sea level muon data only up to several tens of GeV and result in essential deficit of muons at higher energies. As it follows from our examination, uncertainties in muon flux measurements and in the description of nuclear cascades development are not suitable to explain this contradiction, and the only remaining factor, leading to this situation, is underestimation of primary light nuclei fluxes. We have considered systematic effects, that may distort the results of the primary cosmic ray measurements with the application of the emulsion chambers. We suggest, that re-examination of these measurements is required with the employment of different hadronic interaction models. Also, in our point of view, it is necessary to perform estimates of possible influence of the fact, that sizable fraction of events, identified as protons, actually are antiprotons. Study of these cosmic ray component begins to attract much attention, but today nothing definite is known for the energies $>40$ GeV. In any case, to realize whether the mentioned, or some other reasons are the sources of disagreement of the data on primaries with the data on muons, the indicated effects should be thoroughly analyzed

On freeze-out problem in relativistic hydrodynamics

A finite unbound system which is equilibrium in one reference frame is in general nonequilibrium in another frame. This is a consequence of the relative character of the time synchronization in the relativistic physics. This puzzle was a prime motivation of the Cooper--Frye approach to the freeze-out in relativistic hydrodynamics. Solution of the puzzle reveals that the Cooper--Frye recipe is far not a unique phenomenological method that meets requirements of energy-momentum conservation. Alternative freeze-out recipes are considered and discussed.Comment: 6 pages, 2 figures, references are corrected and updated, to be published in the issue of Phys. Atom. Nucl. dedicated to S.T. Belyaev on the occasion of his birthda

Консервативное лечение ятрогенного разрыва трахеи (клинический случай)

The objective was to demonstrate a clinical case of iatrogenic injury of the trachea, which, despite its large size (length 65, width up to 25 mm), wastreated conservatively and, thus, avoided risks for the patient associated with the need for technically complex surgical intervention.Materials and methods. A 65-year-old patient diagnosed with peripheral cancer of the lower lobe of the left lung pT2aN0M0 stage IB, who routinely underwent thoracoscopic left lower lobectomy with mediastinal lymph node dissection. During anesthesia, tracheal intubation with a double-lumen tube of the R. Shaw type was carried out with technical difficulties; during intubation, a defect in the posterior wall of the trachea in its membranous part was formed. The defect was diagnosed on the first postoperative day.Results. Despite the large size of the tracheal defect, the patient had no symptoms of respiratory failure, and there were also no signs of mediastinitis or damage to the esophagus, which almost completely covered the resulting hole in the posterior wall of the trachea. Such circumstances made it possible to avoid a potentially dangerous and complex surgical intervention, carry out conservative therapy and wait for the resulting defect to heal through granulation tissue. Enhanced antimicrobial therapy was carried out; in order to sanitize the tracheobronchial tree and monitor healing, fiber-optic bronchoscopy was performed, which made it possible to clearly demonstrate both the damage itself and the stages of its healing.Conclusions. The described case clearly demonstrates the potential for healing of even very extensive tracheal wall defects with conservative therapy. However, it is important to note that success in this clinical case was the result of a combination of circumstances – only the membranous part of the trachea was damaged; the defect was almost completely covered by the intact esophagus, which reduced the risk of developing mediastinitis and prevented the development of severe pneumomediastinum and subcutaneous emphysema. There were no signs of respiratory failure. The patient was transferred from the intensive care unit on the 13th day of the postoperative period, discharged from the hospital on the 22nd day.Цель – продемонстрировать клинический случай ятрогенного повреждения трахеи, которое, несмотря на крупные размеры (длина 65, ширина до 25 мм), удалось излечить консервативно и, таким образом, избежать рисков для пациента, связанных с необходимостью проведения технически сложного оперативного вмешательства.Материалы и методы. Пациенту 65 лет с диагнозом «Периферический рак нижней доли левого легкого T2aN0M0 IB стадия» в плановом порядке выполнена торакоскопическая нижняя лобэктомия слева с медиастинальной лимфодиссекцией. В ходе анестезии с техническими трудностями проведена интубация трахеи двухпросветной трубкой типа Robertshaw, приведшая к образованию дефекта задней стенки трахеи в мембранозной ее части. Дефект диагностирован в первые послеоперационные сутки.Результаты. У пациента, несмотря на большой размер дефекта трахеи, отсутствовали явления дыхательной недостаточности, а также не было признаков медиастинита и повреждения пищевода, который почти полностью прикрывал образовавшееся отверстие в задней стенке трахеи. Такие обстоятельства позволили избежать потенциально опасного и сложного оперативного вмешательства, провести консервативную терапию и дождаться заживления образовавшегося дефекта через грануляционную ткань. Проводили усиленную антимикробную терапию; с целью санации трахеобронхиального дерева и контроля заживления выполняли фибробронхоскопию, что позволило наглядно продемонстрировать и собственно повреждение, и этапы его заживления.Выводы. Описываемый случай демонстрирует потенциальную возможность заживления даже весьма обширных дефектов стенки трахеи при проведении консервативной терапии. Однако важно отметить, что успех в данном клиническом случае был результатом стечения ряда обстоятельств – повреждена была только мембранозная часть трахеи; дефект практически полностью был прикрыт неповрежденным пищеводом, что уменьшило риск развития медиастинита, предотвратило развитие обширных пневмомедиастинума и подкожной эмфиземы. Также отсутствовали явления дыхательной недостаточности. Пациент был переведен из отделения реанимации и интенсивной терапии на 13-е сутки послеоперационного периода, выписан из стационара на 22-е сутки

Identification of Radiopure Titanium for the LZ Dark Matter Experiment and Future Rare Event Searches

The LUX-ZEPLIN (LZ) experiment will search for dark matter particle interactions with a detector containing a total of 10 tonnes of liquid xenon within a double-vessel cryostat. The large mass and proximity of the cryostat to the active detector volume demand the use of material with extremely low intrinsic radioactivity. We report on the radioassay campaign conducted to identify suitable metals, the determination of factors limiting radiopure production, and the selection of titanium for construction of the LZ cryostat and other detector components. This titanium has been measured with activities of $^{238}$U$_{e}$~$<$1.6~mBq/kg, $^{238}$U$_{l}$~$<$0.09~mBq/kg, $^{232}$Th$_{e}$~$=0.28\pm 0.03$~mBq/kg, $^{232}$Th$_{l}$~$=0.25\pm 0.02$~mBq/kg, $^{40}$K~$<$0.54~mBq/kg, and $^{60}$Co~$<$0.02~mBq/kg (68\% CL). Such low intrinsic activities, which are some of the lowest ever reported for titanium, enable its use for future dark matter and other rare event searches. Monte Carlo simulations have been performed to assess the expected background contribution from the LZ cryostat with this radioactivity. In 1,000 days of WIMP search exposure of a 5.6-tonne fiducial mass, the cryostat will contribute only a mean background of $0.160\pm0.001$(stat)$\pm0.030$(sys) counts.Comment: 13 pages, 3 figures, accepted for publication in Astroparticle Physic