We report on measurements of the Upsilon(1S), Upsilon(2S), and Upsilon(3S) differential cross sections (d(2)sigma/dp(T)dy)(/y/<0.4), as well as on the Upsilon(1S) polarization in p p macro collisions ...at square root of s = 1.8 TeV using a sample of 77+/-3 pb(-1) collected by the collider detector at Fermilab. The three resonances were reconstructed through the decay Upsilon-->mu(+)mu(-). The measured angular distribution of the muons in the Upsilon(1S) rest frame is consistent with unpolarized meson production.
We have performed a search for gluinos (g) and scalar quarks (q) in a data sample of 84 pb(-1) of pp collisions at square roots = 1.8 TeV, recorded by the Collider Detector at Fermilab. We ...investigate the final state of large missing transverse energy and three or more jets, a characteristic signature in R-parity-conserving supersymmetric models. The analysis has been performed "blind," in that the inspection of the signal region is made only after the predictions from standard model backgrounds have been calculated. Comparing the data with predictions of constrained supersymmetric models, we exclude gluino masses below 195 GeV/c2 (95% C.L.), independent of the squark mass. For the case m(q) approximately m(g), gluino masses below 300 GeV/c2 are excluded.
We report a measurement of the strong coupling constant, alpha(s)(MZ), extracted from inclusive jet production in pp collisions at square roots = 1800 GeV. The QCD prediction for the evolution of ...alpha(s) with jet transverse energy ET is tested over the range 40<ET<450 GeV using ET for the renormalization scale. The data show good agreement with QCD in the region below 250 GeV. The value of alpha(s) at the mass of the Z0 boson averaged over the range 40<ET<250 GeV is found to be alpha(s)(MZ) = 0.1178+/-0.0001(stat)+0.0081(-0.0095)(expt. syst). The associated theoretical uncertainties are mainly due to the choice of renormalization scale ((+6%)(-4%)) and input parton distribution functions (5%).
We report a measurement of the diffractive structure function F(D)(jj) of the antiproton obtained from a study of dijet events produced in association with a leading antiproton in pp collisions at ...sqrts = 630 GeV at the Fermilab Tevatron. The ratio of F(D)(jj) at sqrts = 630 GeV to F(D)(jj) obtained from a similar measurement at sqrts = 1800 GeV is compared with expectations from QCD factorization and other theoretical predictions. We also report a measurement of the xi ( x-Pomeron) and beta ( x of parton in Pomeron) dependence of F(D)(jj) at sqrts = 1800 GeV. In the region 0.035<xi<0.095, /t/<1 GeV2, and beta<0.5, F(D)(jj)(beta,xi) is found to be of the form beta(-1.0+/-0.1)xi(-0.9+/-0.1), which obeys beta-xi factorization.
The Collider Detector at Fermilab collected a unique sample of jets originating from bottom-quark fragmentation (\(b\)-jets) by selecting online proton-antiproton (\(p\bar{p}\)) collisions with a ...vertex displaced from the \(p\bar{p}\) interaction point, consistent with the decay of a bottom-quark hadron. This data set, collected at a center-of-mass energy of \(\sqrt{s}=\)1.96 TeV, and corresponding to an integrated luminosity of \(5.4~\rm{fb}^{-1}\), is used to measure the \(Z\)-boson production cross section times branching ratio into \(b\bar{b}\). The number of \(Z\rightarrow b\bar{b}\) events is determined by fitting the dijet-mass distribution while constraining the dominant \(b\)-jet background, originating from QCD multijet events, with data. The result, \(\sigma(p\bar{p} \rightarrow Z) \times \mathcal{B}(Z \rightarrow b\bar{b})= 1.11\pm 0.08(\text{stat}) \pm 0.14(\text{syst})~\text{nb}\), is the most precise measurement of this process, and is consistent with the standard-model prediction. The data set is also used to search for Higgs-boson production. No significant signal is expected in our data and the first upper limit on the cross section for the inclusive \(p\bar p \rightarrow H\rightarrow b\bar b\) process at \(\sqrt{s}=\)1.96 TeV is set, corresponding to 33 times the expected standard-model cross section, or \(\sigma = 40.6\) pb, at the 95\% confidence level.
The Online Silicon Vertex Tracker (SVT) is a new trigger processor dedicated to the 2-D reconstruction of charged particle trajectories at the level 2 of the CDF trigger. The SVT links the digitized ...pulse heights found within the Silicon Vertex Detector to the tracks reconstructed in the Central Outer Tracker by the level 1 Fast Track Finder. The SVT was recently modified in order to increase its efficiency. The new configuration uses all the Silicon Vertex detector layers. On the other hand the processing time has increased. This can be a problem at higher luminosities of the Tevatron. The "Road Warrior" is a new board that, eliminates redundant track candidates before the Track Fitting. It is based on the principle of the Associative Memory. The algorithm used is described in the paper, as well as the hardware implementation.
We present results of the first search for like-sign dilepton ( e(+/-)e(+/-), e(+/-)mu(+/-), mu(+/-)mu(+/-)) events associated with multijets and large missing energy using 106 pb(-1) of data in pp ...macro collisions at square root of s = 1.8 TeV collected during 1992-1995 by the CDF experiment. Finding no events that pass our selection, we examine pair production of gluinos (tilde g) and squarks (tilde q) in a constrained framework of the minimal supersymmetric standard model. At tan beta = 2 and mu = -800 GeV/c(2), we set 95% confidence level limits of M(tilde g)>221 GeV/c(2) for M(tilde g) approximately M(tilde q), and M(tilde q)>168 GeV/c(2) for M(tilde q)>>M(tilde g), both with small variation as a function of mu.
The silicon vertex trigger (SVT) in the CDF experiment at Fermilab performs fast and precise track finding and fitting at the second trigger level and has been a crucial element in data acquisition ...for Run II physics. However as luminosity rises, multiple interactions increase the complexity of events and thus the SVT processing time, reducing the amount of data CDF can record. The SVT upgrade aims to increase the SVT processing power to restore at high luminosity the original CDF DAQ capability. We describe the first steps in the SVT upgrade, consisting of a new associative memory with 4 times the number of patterns, and a new track fitter to take advantage of these patterns. We describe the system, its tests and its performance
The SVT Hit Buffer Belforte, S.; Dell'Orso, M.; Donati, S. ...
IEEE transactions on nuclear science,
06/1996, Letnik:
43, Številka:
3
Journal Article
Recenzirano
The Hit Buffer is part of the Silicon Vertex Tracker 1, a trigger processor dedicated to the reconstruction of particle trajectories in the Silicon Vertex Detector 2 and the Central Tracking Chamber ...of the Collider Detector at Fermilab. The Hit Buffer is a high speed data-traffic node, where thousands of words are received in arbitrary order and simultaneously organised in an internal structured data base, to be later promptly retrieved and delivered in response to specific requests. The Hit Buffer is capable to process data at a rate of 25 MHz, thanks to the use of special fast devices like Cache-Tag RAMs and high performance Erasable Programmable Logic Devices from the XILINX XC7300 family.
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