Photoproduction of D∗±D^{*\pm} mesons associated with a leading neutron

The photoproduction of $D^{*\pm} (2010)$ mesons associated with a leading neutron has been observed with the ZEUS detector in $ep$ collisions at HERA using an integrated luminosity of 80 pb$^{-1}$. The neutron carries a large fraction, {$x_L>0.2$}, of the incoming proton beam energy and is detected at very small production angles, {$\theta_n<0.8$ mrad}, an indication of peripheral scattering. The $D^*$ meson is centrally produced with pseudorapidity {$|\eta| 1.9$ GeV}, which is large compared to the average transverse momentum of the neutron of 0.22 GeV. The ratio of neutron-tagged to inclusive $D^*$ production is $8.85\pm 0.93({\rm stat.})^{+0.48}_{-0.61}({\rm syst.})\%$ in the photon-proton center-of-mass energy range {$130 <W<280$ GeV}. The data suggest that the presence of a hard scale enhances the fraction of events with a leading neutron in the final state.Comment: 28 pages, 4 figures, 2 table

Measurement of the open-charm contribution to the diffractive proton structure function

Production of D*+/-(2010) mesons in diffractive deep inelastic scattering has been measured with the ZEUS detector at HERA using an integrated luminosity of 82 pb^{-1}. Diffractive events were identified by the presence of a large rapidity gap in the final state. Differential cross sections have been measured in the kinematic region 1.5 < Q^2 < 200 GeV^2, 0.02 < y < 0.7, x_{IP} < 0.035, beta 1.5 GeV and |\eta(D*+/-)| < 1.5. The measured cross sections are compared to theoretical predictions. The results are presented in terms of the open-charm contribution to the diffractive proton structure function. The data demonstrate a strong sensitivity to the diffractive parton densities.Comment: 35 pages, 11 figures, 6 table

Search for contact interactions, large extra dimensions and finite quark radius in ep collisions at HERA

A search for physics beyond the Standard Model has been performed with high-Q^2 neutral current deep inelastic scattering events recorded with the ZEUS detector at HERA. Two data sets, e^+ p \to e^+ X and e^- p \to e^- X, with respective integrated luminosities of 112 pb^-1 and 16 pb^-1, were analyzed. The data reach Q^2 values as high as 40000 GeV^2. No significant deviations from Standard Model predictions were observed. Limits were derived on the effective mass scale in eeqq contact interactions, the ratio of leptoquark mass to the Yukawa coupling for heavy leptoquark models and the mass scale parameter in models with large extra dimensions. The limit on the quark charge radius, in the classical form factor approximation, is 0.85 10^-16 cm.Comment: 28 pages, 4 figures, accepted for publication in Physics Letters

Isolated tau leptons in events with large missing transverse momentum at HERA

A search for events containing isolated tau leptons and large missing transverse momentum, not originating from the tau decay, has been performed with the ZEUS detector at the electron-proton collider HERA, using 130 pb^-1 of integrated luminosity. A search was made for isolated tracks coming from hadronic tau decays. Observables based on the internal jet structure were exploited to discriminate between tau decays and quark- or gluon-induced jets. Three tau candidates were found, while 0.40 +0.12 -0.13 were expected from Standard Model processes, such as charged current deep inelastic scattering and single W-boson production. To search for heavy-particle decays, a more restrictive selection was applied to isolate tau leptons produced together with a hadronic final state with high transverse momentum. Two candidate events survive, while 0.20 +-0.05 events are expected from Standard Model processes.Comment: 28 pages, 4 figures, 3 tables, accepted by Phys. Lett. B. Updated with minor changes to the text requested by the journal refere

D* Production in Deep Inelastic Scattering at HERA

This paper presents measurements of D^{*\pm} production in deep inelastic scattering from collisions between 27.5 GeV positrons and 820 GeV protons. The data have been taken with the ZEUS detector at HERA. The decay channel $D^{*+}\to (D^0 \to K^- \pi^+) \pi^+$ (+ c.c.) has been used in the study. The $e^+p$ cross section for inclusive D^{*\pm} production with $5<Q^2<100 GeV^2$ and $y<0.7$ is 5.3 \pms 1.0 \pms 0.8 nb in the kinematic region {$1.3<p_T(D^{*\pm})<9.0$ GeV and $| \eta(D^{*\pm}) |<1.5$}. Differential cross sections as functions of p_T(D^{*\pm}), $\eta(D^{*\pm}), W$ and $Q^2$ are compared with next-to-leading order QCD calculations based on the photon-gluon fusion production mechanism. After an extrapolation of the cross section to the full kinematic region in p_T(D^{*\pm}) and $\eta$(D^{*\pm}), the charm contribution $F_2^{c\bar{c}}(x,Q^2)$ to the proton structure function is determined for Bjorken $x$ between 2 $\cdot$ 10$^{-4}$ and 5 $\cdot$ 10$^{-3}$.Comment: 17 pages including 4 figure

Observation of Scaling Violations in Scaled Momentum Distributions at HERA

Charged particle production has been measured in deep inelastic scattering (DIS) events over a large range of $x$ and $Q^2$ using the ZEUS detector. The evolution of the scaled momentum, $x_p$, with $Q^2,$ in the range 10 to 1280 $GeV^2$, has been investigated in the current fragmentation region of the Breit frame. The results show clear evidence, in a single experiment, for scaling violations in scaled momenta as a function of $Q^2$.Comment: 21 pages including 4 figures, to be published in Physics Letters B. Two references adde

Measurement of dijet photoproduction for events with a leading neutron at HERA

Differential cross sections for dijet photoproduction and this process in association with a leading neutron, e+ + p -> e+ + jet + jet + X (+ n), have been measured with the ZEUS detector at HERA using an integrated luminosity of 40 pb-1. The fraction of dijet events with a leading neutron was studied as a function of different jet and event variables. Single- and double-differential cross sections are presented as a function of the longitudinal fraction of the proton momentum carried by the leading neutron, xL, and of its transverse momentum squared, pT^2. The dijet data are compared to inclusive DIS and photoproduction results; they are all consistent with a simple pion-exchange model. The neutron yield as a function of xL was found to depend only on the fraction of the proton beam energy going into the forward region, independent of the hard process. No firm conclusion can be drawn on the presence of rescattering effects.Comment: 40 pages, 18 figure

Deep inelastic inclusive and diffractive scattering at Q2Q^2 values from 25 to 320 GeV2^2 with the ZEUS forward plug calorimeter

Deep inelastic scattering and its diffractive component, $ep \to e^{\prime}\gamma^* p \to e^{\prime}XN$, have been studied at HERA with the ZEUS detector using an integrated luminosity of 52.4 pb$^{-1}$. The $M_X$ method has been used to extract the diffractive contribution. A wide range in the centre-of-mass energy $W$ (37 -- 245 GeV), photon virtuality $Q^2$ (20 -- 450 GeV$^2$) and mass $M_X$ (0.28 -- 35 GeV) is covered. The diffractive cross section for $2 < M_X < 15$ GeV rises strongly with $W$, the rise becoming steeper as $Q^2$ increases. The data are also presented in terms of the diffractive structure function, $F^{\rm D(3)}_2$, of the proton. For fixed $Q^2$ and fixed $M_X$, \xpom F^{\rm D(3)}_2 shows a strong rise as \xpom \to 0, where \xpom is the fraction of the proton momentum carried by the Pomeron. For Bjorken-$x < 1 \cdot 10^{-3}$, \xpom F^{\rm D(3)}_2 shows positive $\log Q^2$ scaling violations, while for $x \ge 5 \cdot 10^{-3}$ negative scaling violations are observed. The diffractive structure function is compatible with being leading twist. The data show that Regge factorisation is broken.Comment: 89 pages, 27 figure

Observation of Events with an Energetic Forward Neutron in Deep Inelastic Scattering at HERA

In deep inelastic neutral current scattering of positrons and protons at the center of mass energy of 300 GeV, we observe, with the ZEUS detector, events with a high energy neutron produced at very small scattering angles with respect to the proton direction. The events constitute a fixed fraction of the deep inelastic, neutral current event sample independent of Bjorken x and Q2 in the range 3 · 10-4 \u3c xBJ \u3c 6 · 10-3 and 10 \u3c Q2 \u3c 100 GeV2

ФАКТОРЫ ПЕРЕЛИВАНИЯ КРОВИ ПОСЛЕ ЛОБЭКТОМИИ ПЕЧЕНИ У СОБАК И КОШЕК

Liver lobectomy is performed in dogs and cats for the treatment of liver neoplasia, injuries or twist-ing. The dogs and cats undergoing liver lobectomy have a high need for blood transfusion, and higher need for transfusion should be expected in dogs with preoperative anemia and cats with postopera- tive anemia. The research objective was to deter- mine the frequency of blood transfusions, mortality and factors associated with blood transfusions in dogs and cats which had undergone liver lobecto- my. The study was performed on 63 dogs and 9 cats (owned by customers) that had undergone liver lobectomy at specialized veterinary center from August 2013 to June 2018. The data from clin- ical results of blood tests before and after surgery, surgical methods, the number and identity of delet- ed lobes, parallel surgical procedures, hemiabdomens found during operations, blood transfusion rate and survival before discharge from the veterinary clinic (for calculating mortality) were studied. The data were compared between patients who required and did not need blood transfusion. The assessment of potential dependencies be- tween specific factors (age, body weight, preopera- tive hemoabdomain, pre-and postoperative hema- tocrit and also the concentration of solids in blood plasma, surgical method of lobectomy, the number and volume of removed lobes, simultaneous per- formance of other surgical procedures and survival in the clinic before discharge) and the need for pre- operative blood transfusion was given. As a result of researches it was revealed that 11 of 63 (17 %) dogs and 4 of 9 cats needed blood transfusion. The mortality of dogs made 8 %, cats - 22 %. Pre- and postoperative concentration and total solids content in plasma was lower, and the mortality rate was significantly higher in dogs requiring transfusion than in dogs not needing transfusion. Postoperative hematocrit was significantly lower in cats requiring transfusion than in cats not needing transfusion.Лобэктомия печени выполняется у собак и кошек для лечения неоплазии печени, травм или перекручивания. Собаки и кошки, подвер- гающиеся лобэктомии печени, имеют высокую потребность в переливании крови, и более высокую потребность в переливании следует ожидать у собак с предоперационной анемией и у кошек с послеоперационной анемией. Цель исследования - определить частоту перели- вания крови, смертность и факторы, связан- ные с переливанием крови у собак и кошек, пе- ренесших лобэктомию печени. Исследование выполнено на 63 собаках и 9 кошках (принад- лежащих клиентам), которые подверглись ло- бэктомии печени в специализированном вете- ринарном центре с августа 2013 г. по июнь 2018 г. Были изучены данные результатов клинических анализов крови до и после опера- ции, хирургических методов, количества и идентичности удаленных долей, параллельных хирургических процедур, гемоабдомена (обна- руженных во время операций), частоты пере- ливания крови и выживаемости до выписки из ветеринарной клиники (для расчета смертно- сти). Сравнивались данные между пациента- ми, которым требовалось и не требовалось переливание крови. Дана оценка потенциаль- ных зависимостей между специфическимифакторами (возраст, масса тела, предопера- ционный гемоабдомен, до- и послеоперацион- ный гематокрит и концентрация твердых веществ в плазме крови, хирургический метод лобэктомии, количество и объём удаленных долей, одновременное выполнение других хи- рургических процедур, выживание в клинике до выписки) и необходимостью предоперационно- го переливания крови. В результате исследо- ваний выявлено, что 11 из 63 (17%) собак и 4 из 9 кошек нуждались в переливании крови. Смертность собак составила 8 %, кошек - 22 %. До- и послеоперационная концентрация и общее содержание твердых веществ в плаз- ме были ниже, а смертность значительно выше у собак, нуждающихся в переливании крови, чем у собак, не нуждающихся в перели- вании. Послеоперационный гематокрит был значительно ниже у кошек, нуждающихся в трансфузии, чем у кошек, не нуждающихся в трансфузии