A Hadron Blind Detector for the PHENIX Experiment

A novel Hadron Blind Detector (HBD) has been developed for an upgrade of the PHENIX experiment at RHIC. The HBD will allow a precise measurement of electron-positron pairs from the decay of the light vector mesons and the low-mass pair continuum in heavy-ion collisions. The detector consists of a 50 cm long radiator filled with pure CF4 and directly coupled in a windowless configuration to a triple Gas Electron Multiplier (GEM) detector with a CsI photocathode evaporated on the top face of the first GEM foil.Comment: 4 pages, 3 figures, Quark Matter 2005 conference proceeding

Construction and Expected Performance of the Hadron Blind Detector for the PHENIX Experiment at RHIC

A new Hadron Blind Detector (HBD) for electron identification in high density hadron environment has been installed in the PHENIX detector at RHIC in the fall of 2006. The HBD will identify low momentum electron-positron pairs to reduce the combinatorial background in the $e^{+}e^{-}$ mass spectrum, mainly in the low-mass region below 1 GeV/c$^{2}$. The HBD is a windowless proximity-focusing Cherenkov detector with a radiator length of 50 cm, a CsI photocathode and three layers of Gas Electron Multipliers (GEM). The HBD uses pure CF$_{4}$ as a radiator and a detector gas. Construction details and the expected performance of the detector are described.Comment: QM2006 proceedings, 4 pages 3 figure

Scattering in one-dimensional heterostructures described by the Dirac equation

We consider electronic transport accross one-dimensional heterostructures described by the Dirac equation. We discuss the cases where both the velocity and the mass are position dependent. We show how to generalize the Dirac Hamiltonian in order to obtain a Hermitian problem for spatial dependent velocity. We solve exactly the case where the position dependence of both velocity and mass is linear. In the case of velocity profiles, it is shown that there is no backscattering of Dirac electrons. In the case of the mass profile backscattering exists. In this case, it is shown that the linear mass profile induces less backscattering than the abrupt step-like profile. Our results are a first step to the study of similar problems in graphene

High - Temperature Superconductivity in Iron Based Layered Compounds

We present a review of basic experimental facts on the new class of high - temperature superconductors - iron based layered compounds like REOFeAs (RE=La,Ce,Nd,Pr,Sm...), AFe_2As_2 (A=Ba,Sr...), AFeAs (A=Li,...) and FeSe(Te). We discuss electronic structure, including the role of correlations, spectrum and role of collective excitations (phonons, spin waves), as well as the main models, describing possible types of magnetic ordering and Cooper pairing in these compounds.Comment: 43 pages, 30 figures, review talk on 90th anniversary of Physics Uspekh

Polarization transfer in the d(epol,e' ppol)n reaction up to Q^2=1.61 (GeV/c)^2

The recoil proton polarization was measured in the d(epol,e' ppol)n reaction in Hall A of the Thomas Jefferson National Accelerator Facility (JLab). The electron kinematics were centered on the quasielastic peak (x_{Bj}~1) and included three values of the squared four-momentum transfer, Q^2=0.43, 1.00 and 1.61 (GeV/c)^2. For Q^2=0.43 and 1.61 (GeV/c)^2, the missing momentum, p_m, was centered at zero while for Q^2=1.00 (GeV/c)^2 two values of p_m were chosen: 0 and 174 MeV/c. At low p_m, the Q^2 dependence of the longitudinal polarization, P_z', is not well described by a state-of-the-art calculation. Further, at higher p_m, a 3.5 sigma discrepancy was observed in the transverse polarization, P_x'. Understanding the origin of these discrepancies is important in order to confidently extract the neutron electric form factor from the analogous d(epol,e' npol)p experiment.Comment: 6 pages, 4 figures; updated text, figures and table

Superradiance from an ultrathin film of three-level V-type atoms: Interplay between splitting, quantum coherence and local-field effects

We carry out a theoretical study of the collective spontaneous emission (superradiance) from an ultrathin film comprised of three-level atoms with $V$-configuration of the operating transitions. As the thickness of the system is small compared to the emission wavelength inside the film, the local-field correction to the averaged Maxwell field is relevant. We show that the interplay between the low-frequency quantum coherence within the subspace of the upper doublet states and the local-field correction may drastically affect the branching ratio of the operating transitions. This effect may be used for controlling the emission process by varying the doublet splitting and the amount of low-frequency coherence.Comment: 15 pages, 5 figure

ОРГАНОСОХРАНЯЮЩЕЕ ЛЕЧЕНИЕ РАКА ПРЯМОЙ КИШКИ

Objective: to evaluate the results of “watch and wait” approach for rectal cancer patients with complete clinical response after neoadjuvant chemoradiotherapy (CRT) followed by consolidation chemotherapy.Materials and methods. Between 2013 and 2016, 130 patients who were diagnosed with stage T2N0–1M0–T3(CRM+)–4N0–2M0 middle and low rectal cancer were treated by CRT (single dose 2 Gy to a total dose 50–54 Gy with concominant capecitabine 850 mg/m2 /day of radiotherapy) with consolidation chemotherapy (CapOx) (capecitabine 2000 mg/m2 14 days and oxaliplatin 130 mg/m2 intravenous once in 3 weeks).Results. 21 patient showed complete clinical response. During the time of observation (median 14.6 month) all patients alive without signs of recurrence and progression.Conclusion. Preliminary results showed that organ saving treatment for rectal cancer patients with a complete clinical response is oncologically safe when followed by strict selection criteria and active follow-up, including endoscopy and magnetic resonance imagin. Future investigation is needed to justify this statement. Probability of complete response is higher for early stages of rectal cancer. Цель работы – изучить результаты лечения больных раком прямой кишки с полным клиническим ответом после проведенной неоадъювантной химиолучевой терапии (ХЛТ) с консолидирующей химиотерапией (ХТ) при выжидательной тактике с активным динамическим наблюдением.Материалы и методы. В период с 2013 по2016 г. 130 пациентов с раком нижнеи среднеампулярного отделов прямой кишки стадий T2N0–1M0 –T3(CRM+)– 4N0–2M0 вошли в исследование. ХЛТ проводили фракциями по 2 Гр до суммарной очаговой дозы 50–54 Гр на фоне приема капецитабина 850 мг/м2 /сут в дни облучения. В период 12 нед после окончания ХЛТ пациентам проводилась консолидирующая ХТ по схеме CapOx (2 курса, капецитабин 2000 мг/м2 в течение 14 дней и оксалиплатин 130 мг/м2 внутривенно 1 раз в 3 нед).Результаты. Из 130 пациентов у 21 зарегистрирован полный клинический ответ. За период наблюдения (медиана 14,6 мес) все больные живы без признаков локорегионарного рецидивирования или прогрессирования заболевания.Выводы. Предварительные результаты нашего исследования показали онкологическую безопасность органосохраняющего лечения больных раком прямой кишки с полным клиническим ответом после неоадъювантной ХЛТ при строгом соблюдении критериев отбора и активном динамическом наблюдении, включающем эндоскопическое исследование и магнитно-резонансный контроль. Для окончательных выводов требуются дальнейшие исследования. Вероятность полного клинического ответа выше у пациентов с ранними стадиями рака прямой кишки.

Thermal Dileptons at LHC

We predict dilepton invariant-mass spectra for central 5.5 ATeV Pb-Pb collisions at LHC. Hadronic emission in the low-mass region is calculated using in-medium spectral functions of light vector mesons within hadronic many-body theory. In the intermediate-mass region thermal radiation from the Quark-Gluon Plasma, evaluated perturbatively with hard-thermal loop corrections, takes over. An important source over the entire mass range are decays of correlated open-charm hadrons, rendering the nuclear modification of charm and bottom spectra a critical ingredient.Comment: 2 pages, 2 figures, contributed to Workshop on Heavy Ion Collisions at the LHC: Last Call for Predictions, Geneva, Switzerland, 14 May - 8 Jun 2007 v2: acknowledgment include