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Biomedical subjects

V Bhatnagar

Publications and source records attributed to V Bhatnagar.

At least 37 records · Page 2Linked to original sources

Search for Randall-Sundrum gravitons in dilepton and diphoton final states.

We report the first direct search for the Kaluza-Klein (KK) modes of Randall-Sundrum gravitons using dielectron, dimuon, and diphoton events observed with the D0 detector operating at the Fermilab Tevatron pp(-) Collider at sqrt[s]=1.96 TeV. No evidence for resonant production of gravitons has been found in the data corresponding to an integrated luminosity of approximately equal to 260 pb(-1). Lower limits on the mass of the first KK mode at the 95% C.L. have been set between 250 and 785 GeV, depending on its coupling to standard model particles.

Journal Article↗

Study of Zgamma events and limits on anomalous ZZgamma and Zgammagamma couplings in pp collisions at square root s = 1.96 TeV.

We present a measurement of the Zgamma production cross section and limits on anomalous ZZgamma and Zgammagamma couplings for form-factor scales of lambda = 750 and 1000 GeV. The measurement is based on 138 (152) candidates in the eegamma (mumugamma) final state using 320(290) pb(-1) of pp(-1) collisions at square root of s = 1.96 TeV. The 95% C.L. limits on real and imaginary parts of individual anomalous couplings are /h(10,30)Z/ < 0.23, /h(20,40)Z/ < 0.020, /h(10,30)gamma/ < 0.23, and /h(20,40)gamma/ < 0.019 for lambda = 1000 GeV.

Journal Article↗

Measurement of inclusive differential cross sections for pp collisions at (square root)s = 1.96 TeV.

We present measurements of the inclusive production cross sections of the Gamma(1S) bottomonium state in pp collisions at (square root)s = 1.96 TeV. Using the Gamma(1S) --> mu(+)mu(-) decay mode for a data sample of 159 +/- 10 pb(-1) collected by the D0 detector at the Fermilab Tevatron collider, we determine the differential cross sections as a function of the Gamma(1S) transverse momentum for three ranges of the Gamma(1S) rapidity: 0 < y(Gamma) < or = 0.6, 0.6 < y(Gamma) < or = 1.2, and 1.2 < y(Gamma) < or = 1.8.

Journal Article↗

Measurement of dijet azimuthal decorrelations at central rapidities in pp collisions at sqrt s =1.96 TeV.

Correlations in the azimuthal angle between the two largest transverse momentum jets have been measured using the D0 detector in p (-)p collisions at a center-of-mass energy sqrt[s]=1.96 TeV. The analysis is based on an inclusive dijet event sample in the central rapidity region corresponding to an integrated luminosity of 150 pb(-1). Azimuthal correlations are stronger at larger transverse momenta. These are well described in perturbative QCD at next-to-leading order in the strong coupling constant, except at large azimuthal differences where contributions with low transverse momentum are significant.

Journal Article↗

Measurement of the ratio of B+ and B0 meson lifetimes.

The ratio of the B+ and B0 meson lifetimes was measured using data collected in 2002-2004 by the D0 experiment in Run II of the Fermilab Tevatron Collider. These mesons were reconstructed in B-->mu(+)nuD(*-)X decays, which are dominated by B0 and B-->mu(+)nuD 0X decays, which are dominated by B+. The ratio of lifetimes is measured to be tau(+)/tau(0)=1.080+/-0.016(stat)+/-0.014(syst).

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Measurement of the ratio of inclusive cross sections sigma(pp --> Z + b jet)/sigma(pp --> Z + jet) at square root(s) = 1.96 TeV.

Using the data collected with the D0 detector at square root(s) = 1.96 TeV, for integrated luminosities of about 180 pb(-1), we have measured the ratio of inclusive cross sections for pp --> Z + b jet to pp --> Z + jet production. The inclusive Z + b-jet reaction is an important background to searches for the Higgs boson in associated ZH production at the Fermilab Tevatron collider. Our measurement is the first of its kind, and relies on the Z --> e+ e- and Z --> mu+ mu- modes. The combined measurement of the ratio yields 0.021+/-0.005 for hadronic jets with transverse momenta pT > 20 GeV/c and pseudorapidities absolute value(eta) < 2.5, consistent with next-to-leading-order predictions of the standard model.

Journal Article↗

Search for anomalous heavy-flavor quark production in association with W bosons.

We search for anomalous production of heavy-flavor quark jets in association with W bosons at the Fermilab Tevatron pp Collider in final states in which the heavy-flavor quark content is enhanced by requiring at least one tagged jet in an event. Jets are tagged using one algorithm based on semileptonic decays of b/c hadrons, and another on their lifetimes. We compare e+jets (164 pb(-1)) and mu+jets (145 pb(-1)) channels collected with the D0 detector at sqrt[s]=1.96 TeV to expectations from the standard model and set upper limits on anomalous production of such events.

Journal Article↗

Measurement of the WW production cross section in pp collisions at square root[s]=1.96 TeV.

We present a measurement of the W boson pair-production cross section in pp collisions at a center-of-mass energy of sqrt[s]=1.96 TeV. The data, collected with the Run II D0 detector at Fermilab, correspond to an integrated luminosity of 224-252 pb(-1) depending on the final state (ee, emu, or mumu). We observe 25 candidates with a background expectation of 8.1+/-0.6(stat)+/-0.6(syst)+/-0.5(lum) events. The probability for an upward fluctuation of the background to produce the observed signal is 2.3x10(-7), equivalent to 5.2 standard deviations. The measurement yields a cross section of 13.8(+4.3)(-3.8)(stat)+1.2-0.9(syst)+/-0.9(lum) pb, in agreement with predictions from the standard model.

Journal Article↗

Measurement of the Lambda0b lifetime in the decay lambda0b--> J/psiLambda0 with the D0 detector.

We present measurements of the Lambda(0)(b) lifetime in the exclusive decay channel Lambda(0)(b)--> J/psiLambda(0), with J/psi--> mu(+)mu(-) and Lambda(0)--> ppi(-), the B0 lifetime in the decay B0-->J/psiK(0)(S) with J/psi--> mu(+)mu(-) and K(0)(S)-->pi(+)pi(-), and the ratio of these lifetimes. The analysis is based on approximately 250 pb(-1) of data recorded with the D0 detector in pp collisions at sqrt[s] = 1.96 TeV. The Lambda(0)(b) lifetime is determined to be tau(Lambda(0)(b)) = 1.22(+0.22)(-0.18)(stat) +/- 0.04(syst) ps, the B0 lifetime tau(B0) = 1.40(+0.11)(-0.10)(stat) +/- 0.03(syst) ps, and the ratio tau(Lambda(0)(b))/tau(B0) = 0.87(+0.17)(-0.14)(stat) +/- 0.03(syst). In contrast with previous measurements using semileptonic decays, this is the first determination of the Lambda(0)(b) lifetime based on a fully reconstructed decay channel.

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Search for Wbb and WH production in pp collisions at square root [s]=1.96 TeV.

We present a search for Wbb production in pp collisions at sqrt[s]=1.96 TeV in events containing one electron, an imbalance in transverse momentum, and two b-tagged jets. Using 174 pb(-1) of integrated luminosity accumulated by the D0 experiment at the Fermilab Tevatron collider, and the standard-model description of such events, we set a 95% C.L. upper limit on Wbb production of 6.6 pb for b quarks with transverse momenta p(b)(T)>20 GeV and bb separation in pseudorapidity-azimuth space DeltaR(bb)>0.75. Restricting the search to optimized bb mass intervals provides upper limits on WH production of 9.0-12.2 pb for Higgs-boson masses of 105-135 GeV.

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Search for the flavor-changing neutral current decay B0s--> mu(+) mu(-) in pp Collisions at sqrt[s] = 1.96 TeV with the D0 detector.

We present the results of a search for the flavor-changing neutral current decay B(0)(s)--> mu(+) mu(-) using a data set with integrated luminosity of 240 pb(-1) of pp collisions at sqrt[s] = 1.96 TeV collected with the D0 detector in run II of the Fermilab Tevatron collider. We find the upper limit on the branching fraction to be B(B(0)(s)--> mu(+) mu(-)) < or= 5.0 x 10(-7) at the 95% C.L. assuming no contributions from the decay B(0)(d)--> mu(+) mu(-) in the signal region. This limit is the most stringent upper bound on the branching fraction B(0)(s)--> mu(+) mu(-) to date.

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Measurement of the B0s lifetime in the exclusive decay channel B0s-->J/psiphi.

Using the exclusive decay B0s-->J/psi(mu+mu-)phi(K+K-), we report the most precise single measurement of the B0s lifetime. The data sample corresponds to an integrated luminosity of approximately 220 pb(-1) collected with the D0 detector at the Fermilab Tevatron Collider in 2002-2004. We reconstruct 337 signal candidates, from which we extract the B0s lifetime, tau(B0s)=1.444(+0.098)(-0.090)(stat)+/-0.020(sys) ps. We also report a measurement for the lifetime of the B0 meson using the exclusive decay B0-->J/psi(mu+mu-)K*0(892)(K+pi-). We reconstruct 1370 signal candidates, obtaining tau(B0)=1.473(+0.052)(-0.050)(stat)+/-0.023(sys) ps, and the ratio of lifetimes, tau(B0s)/tau(B0)=0.980(+0.076)(-0.071)(stat)+/-0.003(sys).

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Search for supersymmetry with gauge-mediated breaking in diphoton events at D0.

We report the results of a search for supersymmetry (SUSY) with gauge-mediated breaking in the missing transverse energy distribution of inclusive diphoton events using 263 pb(-1) of data collected by the D0 experiment at the Fermilab Tevatron Collider in 2002-2004. No excess is observed above the background expected from standard model processes, and lower limits on the masses of the lightest neutralino and chargino of about 108 and 195 GeV, respectively, are set at the 95% confidence level. These are the most stringent limits to date for models with gauge-mediated SUSY breaking with a short-lived neutralino as the next-to-lightest SUSY particle.

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Anorectal malformations and their impact on survival.

OBJECTIVE: To evaluate the incidence, types and the effect on outcome of associated anomalies in neonates with anorectal malformations (ARM). METHODS: This retrospective study was carried out on all neonates with ARM admitted to the neonatal surgical intensive care unit (NSICU) from 1998 through 2003. RESULTS: Of the 754 neonates admitted to the NSICU during the study period of 6 years, there were 124 (16.4%) neonates with anorectal malformations. Of these 110 were included in the study. 73 % were male and 27% female. 86% of these were high ARM (HARM) while only 14% were low ARM (LARM). Associated anomalies were seen in 68% of patients. The incidence was 72% for HARM and 50% for LARM. The major associated anomalies consisted of esophageal (13%), gastrointestinal (GIT) (11%), genitourinary (GUT) (32%), skeletal (26%), cardiac (33%) and miscellaneous 26%. The overall survival rate was 84% (82% for HARM and 94% for LARM). The survival among those with associated esophageal anomalies was 43%, GIT 67%, GUT 80%, cardiac 61%, skeletal 76% and miscellaneous 79% respectively. This difference in survival was significant only for those with esophageal (p=0.004) and cardiac anomalies (p=0.0026). The survival rates among those with one, two or more than two organ systems involved with associated anomalies were 88%, 82% and 58% respectively. This difference was significant only for more than two organ systems involvement (p=0.003). CONCLUSION: Associated anomalies are common in neonates with ARM, the incidence being similar for HARM and LARM. The survival depends upon the number and severity of associated anomalies both in patients with LARM and HARM. Neonates with more number of organ systems involved have a poorer survival specially when associated with esophageal and cardiac anomalies. All neonates with ARM merit a meticulous search for associated anomalies so that the management can be tailored for each baby.

Abnormalities, Multiple↗

Respiratory distress in neonates.

Respiratory distress due to either medical or surgical causes occurs commonly in neonates. It is the most common cause of admission to a neonatal surgical intensive care facility in a tertiary care hospital. The distress can be caused by a variety of clinical conditions; common conditions treated in medical intensive care units are transient tachypnea of the new born, respiratory distress syndrome, pulmonary air leak and pneumothorax. In surgical causes of respiratory distress in neonates the underlying mechanisms include airway obstruction, pulmonary collapse or displacement and parenchymal disease or insufficiency; the common causes are congenital diaphragmatic hernia, congenital cystic adenomatoid malformation, congenital lobar emphysema and esophageal atresia with or without tracheo-esophageal fistula. Obstructive lesions of the new born airway include choanal atresia, macroglossis, Pierre-Robin syndrome, lymphangioma, teratoma or other mediastinal masses, cysts, subglottic stenosis and laryngo tracheomalacia. Imaging plays a very major role in the pre-operative diagnosis of these conditions and proper pre-operative resuscitation helps in improving the results of surgery dramatically.

Airway Obstruction↗

Urodynamics-based evidence for the beneficial effect of imipramine on valve bladders in children.

AIMS: In an era, in which valve bladder is recognised as perhaps the single most important determinant of long-term outcome in patients with posterior urethral valves (PUV), an insight into the etiopathogenesis and management of valve bladders is warranted. The present study was designed to evaluate bladder dysfunction in PUV and to assess the response to imipramine in these patients, both subjectively and objectively, by serial urodynamic studies (UDS). METHODS: From 1998-2001, 30 patients with PUV who had documented bladder dysfunction on UDS were studied. Patients with non-compliant or unstable bladders were treated with imipramine (1.5 - 2 mg/kg). All the patients in the present study were 5 years or older and hence old enough to be toilet trained. Assessment of continence and side effects of the drug was done after 3 months and repeat UDS were done at 3-6 months, 1 and 2 years. RESULTS: On the basis of initial treatment, the patients were divided into 2 groups; a fulguration group (n = 10, 33.3 %) and a vesicostomy group (n = 20, 66.6 %). Symptomatic voiding dysfunction was present in 27 of the 30 patients (90 %). Two patterns of urodynamic abnormalities were noted in the present study; 1) unstable bladders with single or multiple uninhibited contractions (18/30 patients, 60 %), and 2) small capacity, hypocompliant, hypertonic bladder (12/30 patients, 40 %). Post imipramine therapy significant symptomatic improvement was noted in 16/30 patients. On serial UDS, there was a 18-20 % increase in maximum cystometric capacity (MCC) and 30-35 % increase in pressure specific bladder volume (PSBV) following one year of imipramine therapy in 16/30 patients and 11/30 patients, respectively. 4 patients failed to show any improvement in MCC and PSBV with imipramine, they had been initially diverted with vesicostomy and later required augmentation cystoplasty. CONCLUSION: Unstable bladders and those with marginal bladder capacity and compliance showed the best response to imipramine therapy. Fibrotic, small capacity, hypertonic bladders are less responsive to imipramine. However, a trial of imipramine therapy is still warranted in these patients, as only 4/12 (33.3 %) patients with fibrotic hypertonic bladders failed to show any response and ultimately required augmentation cystoplasty. Imipramine qualifies as an effective and cheap drug for valve bladders.

Adrenergic Uptake Inhibitors↗

Electrocardiographic and biochemical evidence for the cardioprotective effect of vitamin E in doxorubicin-induced acute cardiotoxicity in rats.

BACKGROUND/AIMS: Cardiotoxicity is a major side effect limiting the use of doxorubicin, a potent chemotherapeutic agent, in the treatment of pediatric neoplastic diseases. The effect of vitamin E in doxorubicin-induced cardiotoxicity in rats has been studied. METHODS: Eighteen Wistar male rats (age 60 - 100 days, weighing 175 - 260 g) were divided into three groups of six: group A (controls); group B (doxorubicin-treated rats); and group C (pretreatment with a high dose of vitamin E followed by doxorubicin treatment). The weights of the rats were measured daily. The rats were sacrificed seven days after the last dose of doxorubicin injection by an overdose of ether. Electrocardiogram (ECG) tracings were recorded before sacrificing the rats. The ECG tracings were then evaluated for rate and rhythm disorders by assessing the PR, ST, and QT intervals. In group B rats ECG tracings were taken three days after the completion of doxorubicin treatment, while in group C rats they were taken at the end of 2 weeks of vitamin E pretreatment and again 3 days after the completion of doxorubicin treatment. Serum levels of creatine phosphokinase (CPK-MB), lactic dehydrogenase (LDH), and serum glutamic oxaloacetic transaminase (SGOT) were assessed from an intracardiac blood sample taken at the time of sacrificing the rat. RESULTS: Mean weight ranged from 205 - 226 g. Mean total dose of doxorubicin in groups B and C ranged from 36 - 38 mg. The PR intervals in the three groups were recorded as 0.006, 0.070, 0.057 s for groups A, B, and C, respectively (p = 0.0024) and the QT interval as 0.023, 0.120, 0.088 s in groups A, B, and C, respectively (p = 0.00089). The ST elevation due to doxorubicin toxicity was significantly reversed by vitamin E treatment. The difference in the levels of CPK-MB and LDH between the three groups was found to be statistically significant. Serum SGOT levels also varied between the three groups but were not statistically significant. CONCLUSION: Vitamin E pretreatment prevented the PR, QT, and ST segment changes caused by doxorubicin. Vitamin E treatment helped to decrease the levels of CPK-MB and LDH that were increased due to myocardial damage caused by the doxorubicin. There is sufficient evidence to believe that vitamin E protects the rat myocardium from doxorubicin-induced damage.

Animals↗

Observation and properties of the X(3872) decaying to J/psipi(+)pi(-) in pp collisions at sqrt[s]=1.96 TeV.

We report the observation of the X(3872) in the J/psipi(+)pi(-) channel, with J/psi decaying to mu(+)mu(-), in pp collisions at sqrt[s]=1.96 TeV. Using approximately 230 pb(-1) of data collected with the Run II D0 detector, we observe 522+/-100 X(3872) candidates. The mass difference between the X(3872) state and the J/psi is measured to be 774.9+/-3.1(stat)+/-3.0(syst) MeV/c(2). We have investigated the production and decay characteristics of the X(3872) and find them to be similar to those of the psi(2S) state.

Journal Article↗