Biomedical subjects
Publications and source records attributed to M Buehler.
We present a search for charged Higgs bosons in decays of pair-produced top quarks in pp collisions at sqrt[s] = 1.8 TeV recorded by the D0 detector at the Fermilab Tevatron collider. With no evidence for signal, we exclude most regions of the ( M(H+/-),tan(beta)) parameter space where the decay t--> H(+)b has a branching fraction >0.36 and B(H+/--->tau(nu)(tau)) is large.
The inclusive cross section for production of isolated photons has been measured in pp macro collisions at square root of s = 630 GeV with the D0 detector at the Fermilab Tevatron Collider. The photons span a transverse energy (E(T)) range from 7-49 GeV and have pseudorapidity absolute value of eta < 2.5. This measurement is combined with the previous D0 result at square root of s = 1800 GeV to form a ratio of the cross sections. Comparison of next-to-leading-order QCD with the measured cross section at 630 GeV and the ratio of cross sections show satisfactory agreement in most of the E(T) range.
We describe QUAERO, a method that (i) enables the automatic optimization of searches for physics beyond the standard model, and (ii) provides a mechanism for making high energy collider data generally available. We apply QUAERO to searches for standard model WW, ZZ, and t t macro production, to searches for these objects produced through a new heavy resonance, and to the first direct search for W'-->WZ. Through this interface, we make three data sets collected by the D0 experiment at square root of [s] = 1.8 TeV publicly available.
We present results of searches for technirho (rho(T)), techniomega (omega(T)), and Z' particles, using the decay channels rho(T),omega(T),Z'-->e(+)e(-). The search is based on 124.8 pb(-1) of data collected by the D0 detector at the Fermilab Tevatron during 1992-1996. In the absence of a signal, we set 95% C.L. upper limits on the cross sections for the processes pp-->rho(T),omega(T),Z'-->e(+)e(-) as a function of the mass of the decaying particle. For certain model parameters, we exclude the existence of degenerate rho(T) and omega(T) states with masses below about 200 GeV. We exclude a Z' with mass below 670 GeV, assuming that it has the same couplings to fermions as the Z boson.
We apply a quasi-model-independent strategy ("Sleuth") to search for new high p(T) physics in approximately 100 pb(-1) of pp collisions at square root of (s) = 1.8 TeV collected by the D0 experiment during 1992-1996 at the Fermilab Tevatron. We systematically analyze many exclusive final states and demonstrate sensitivity to a variety of models predicting new phenomena at the electroweak scale. No evidence of new high p(T) physics is observed.
The D0 Collaboration has measured the inclusive jet cross section in barpp collisions at square root of s = 630 GeV. The results for pseudorapidities (eta)<0.5 are combined with our previous results at square root of s = 1800 GeV to form a ratio of cross sections with smaller uncertainties than either individual measurement. Next-to-leading-order QCD predictions show excellent agreement with the measurement at 630 GeV; agreement is also satisfactory for the ratio. Specifically, despite a 10% to 15% difference in the absolute magnitude, the dependence of the ratio on jet transverse momentum is very similar for data and theory.
We report on a study of the ratio of inclusive three-jet to inclusive two-jet production cross sections as a function of total transverse energy in p&pmacr; collisions at a center-of-mass energy sqrt[s] = 1.8 TeV, using data collected with the D0 detector during the 1992-1993 run of the Fermilab Tevatron Collider. The measurements are used to deduce preferred renormalization scales in perturbative O(alpha(3)(s)) QCD calculations in modeling soft-jet emission.
We report a new measurement of the pseudorapidity (eta) and transverse-energy ( E(T)) dependence of the inclusive jet production cross section in pp(macro) collisions at square root of s = 1.8 TeV using 95 pb(-1) of data collected with the D0 detector at the Fermilab Tevatron. The differential cross section d(2)sigma/(dE(T)d eta) is presented up to eta = 3, significantly extending previous measurements. The results are in good overall agreement with next-to-leading order predictions from QCD and indicate a preference for certain parton distribution functions.
We report a search for effects of large extra spatial dimensions in pp collisions at a center-of-mass energy of 1.8 TeV with the D0 detector, using events containing a pair of electrons or photons. The data are in good agreement with the expected background and do not exhibit evidence for large extra dimensions. We set the most restrictive lower limits to date, at the 95% C.L. on the effective Planck scale between 1.0 and 1.4 TeV for several formalisms and numbers of extra dimensions.
BACKGROUND: We set out to analyze the technical aspects, intraoperative complications, morbidity, and mortality of laparoscopic cholecystectomy in a multi-institutional study representative of Switzerland. METHODS: Data were collected from 10,174 patients from 82 surgical services. A total of 353 different parameters per patient were included. RESULTS: We found intraoperative complications in 34.4% of patients and had a conversion rate of 8.2%. This rate was significantly increased in patients with complicated cholelithiasis and in those with previous upper-but not lower-abdominal surgery. In most cases, conversions to open procedures were required because of technical difficulties due to inflammatory changes and/or unclear anatomical findings at the time of operation. Bleeding was a common intraoperative complication, that significantly increased the risk of conversion. Patients with loss of gallstones in the peritoneal cavity had increased rates of abscesses. The rate of common bile duct injuries was 0.31%, but it decreased significantly as the laparoscopic experience of the surgeon increased. The rate of common bile duct injuries was not increased in patients with acute cholecystitis or in the 1.32% of patients undergoing laparoscopic common bile duct exploration. Intraoperative cholangiography did not reduce the risk of common bile duct injuries, but it allowed them to be diagnosed intraoperatively in 75% of patients. Local complications were recorded in 4.79% of patients, and systemic complications were seen in 5.59%. The mortality rate was 0.2%. CONCLUSIONS: Although laparoscopic cholecystectomy is a safe procedure, the rate of conversion to open cholecystectomy is still substantial. The conversion rate depends both on the indication and intraoperative complications. There is still a 10.38% morbidity associated with the procedure; however, the incidence of common bile duct injuries, which decreases with growing laparoscopic experience, was relatively low.
OBJECTIVE: To discuss a case of osteoid osteoma of the vertebral body with extension across the disc space, a very rare location and unique finding. FEATURES: An 18-yr-old man suffered midthoracic pain that was thought to be related to a lifting injury. However, further evaluation revealed an osteoid osteoma of the T6 vertebral body. Special imaging revealed extension of the inflammatory component across the intervertebral disc involving the adjacent vertebral body. INTERVENTION AND OUTCOME: The patient underwent vertebrectomy (resection of the osteoid osteoma) via a transpleural approach with T5 disc resection, sixth rib resection and rib strut graft insertion. Complete relief of the symptoms was reported almost immediately after surgery. CONCLUSION: The vertebral body is a very unusual location for an osteoid osteoma and extension across the intervertebral disc is a unique finding. Surgical resection of the entire nidus yields optimum results.
The association of posterior leg sepsis with pyogenic arthritis of the knee is rare, but nevertheless the diagnosis should be kept in mind. Calf swelling and tenderness with apparent antibiotic resistance in pyogenic arthritis of the knee are the major signs of the diagnosis. Ultrasound, computerized axial tomography, or aspiration of the posterior compartment may show fluid in the posterior compartment. Clinical examination is the most dependable method of diagnosis. Treatment consists of adequate surgical drainage of the posterior compartment and appropriate antibiotic therapy.
Benign Osteoblastomas are uncommon tumors which make up approximately 1 percent of all bone tumors. The distribution of the tumor demonstrates a high incidence for spinal involvement. This case report shows an osteoblastoma in a somewhat unusual location of the cervical spine, the posterior arch of the atlas.
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