A. Canepa

Search for Bs0â†Î+Î- and Bd0â†Î +Î- Decays in pp Collisions with CDF II

We report on a search for Bs ->mu+mu- and Bd ->mu+mu- decays in ppbar collisions at sqrt(S) = 1.96 TeV using 364 pb-1 of data collected by the CDF II detector at the Fermilab Tevatron Collider. After applying all selection requirements, we observe no candidates inside the Bs or Bd mass windows, consistent with the background expectation. The resulting upper limits on the branching fractions are B(Bs ->mu+mu-)<1.5E10-7 and B(Bd ->mu+mu-)<3.9E-8 at 90% confidence level.

Level-2 calorimeter Trigger Upgrade at CDF

The CDF Run II Level-2 calorimeter trigger is implemented in hardware and is based on an algorithm used in Run I. This system insured good performance at low luminosity obtained during the Tevatron Run II. However, as the Tevatron instantaneous luminosity increases, the limitations of the current system due to the algorithm start to become clear. In this paper, we will present an upgrade of the Level-2 calorimeter trigger system at CDF. The upgrade is based on the Pulsar board, a general purpose VME board developed at CDF and used for upgrading both the Level-2 tracking and the Level-2 global decision crate. This paper will describe the design, hardware and software implementation, as well as the advantages of this approach over the existing system.

Measurement of the W+W- production cross section in pp̄ collisions at s=1.96TeV using dilepton events

We present a measurement of the W(+)W(-) production cross section using 184 pb(-1) of p(p) collisions at a center-of-mass energy of 1.96 TeV collected with the Collider Detector at Fermilab. Using the dilepton decay channel W(+)W(-)-->l(+)nul(-), where the charged leptons can be either electrons or muons, we find 17 candidate events compared to an expected background of 5.0(+2.2)(-0.8) events. The resulting W(+)W(-) production cross-section measurement of sigma(pp-->W(+)W(-))=14.6(+5.8)(-5.1)(stat)(+1.8)(-3.0)(syst) +/- 0.9(lum) pb agrees well with the standard model expectation.We present a measurement of the W+W- production cross section using 184/pb of ppbar collisions at a center-of-mass energy of 1.96 TeV collected with the Collider Detector at Fermilab. Using the dilepton decay channel W+W- ->l+l-vvbar, where the charged leptons can be either electrons or muons, we find 17 candidate events compared to an expected background of 5.0+2.2-0.8 events. The resulting W+W- production cross section measurement of sigma(ppbar ->W+W-) = 14.6 +5.8 -5.1 (stat) +1.8 -3.0 (syst) +-0.9 (lum) pb agrees well with the Standard Model expectation.

Level-3 calorimeter resolution available for the Level-1 and Level-2 CDF triggers

As the Tevatron luminosity increases more sophisticated selections are required to be efficient in selecting rare events from a very huge background. To cope with this problem, CDF has pushed the Level-3 calorimeter algorithm resolutions up to Level-2 and, when possible, at Level-1, increasing efficiency and, at the same time, keeping under control the rates. This strategy increases the purity of the Level-2 and Level-1 samples, produces free-bandwidth that allows to reduce the thresholds. The global effect is an increase of the signal efficiency of important Tevatron Standard Model Higgs search channels (H → WW, ZH, WH). The L2 upgrade improves the cluster finding algorithm, the resolution of the Missing Transverse Energy (MET) and the SUM Transverse Energy (SUMET) calculations. The same Level-2 MET and SUMET improved resolution has been made available to the Level-1 system, exploiting the same hardware used for the Level-2 upgrade. The upgrade is based on the Pulsar board, a general purpose VME board developed at CDF and already used for upgrading both the Level-2 tracking and the Level-2 global decision crate. The Level-2 upgrade has been designed, built, tested and commissioned in six months. It was accepted as the default system for CDF in August 2007. The same Level-2 hardware can be used in such a way to provide the Level-1 calorimeter system of the same MET, SUMET resolution provided to Level-2. While in the upgraded Level-2 system the algorithms are executed in a commercial CPU within the typical Level-2 processing timing of 20 μs, in the upgraded Level-1 system, MET and SUMET are calculated by powerful FPGAs within 5 μs. The Level-1 upgrade is currently ongoing and in commissioning phase.We describe the CDF Level-2 and the new Level-1 calorimeter upgrades, the architecture and the trigger performances, with particular emphasis on a new calorimeter MET_JET-based trigger performances used for CDF Higgs search.

Search for the flavor-changing neutral current decay D0→ μ+μ-in pp̄ collisions at √s = 1.96TeV

We report on a search for the flavor-changing neutral current decay D/sup 0/ to mu /sup +/ mu /sup -/ in pp collisions at square root s=1.96 TeV using 65 pb/sup -1/ of data collected by the CDF II experiment at the Fermilab Tevatron Collider. A displaced-track trigger selects long-lived D/sup 0/ candidates in the D/sup 0/ to mu /sup +/ mu /sup -/ search channel, the kinematically similar D/sup 0/ to pi /sup +/ pi /sup -/ channel used for normalization, the Cabibbo-favored D/sup 0/ to K/sup -/ pi /sup +/ channel used to optimize the selection criteria in an unbiased manner, and their charge conjugates. Finding no signal events in the D/sup 0/ to mu /sup +/ mu /sup -/ search window, we set an upper limit on the branching fraction B(D/sup 0/ to mu /sup +/ mu /sup -/) lt or=2.5*10/sup -6/ (3.3*10/sup -6/) at the 90% (95%) confidence level.

Level-2 Calorimeter Trigger Upgrade at CDF

The CDF Run II level 2 calorimeter trigger is implemented in hardware and is based on a simple algorithm that was used in Run I. This system has worked well for Run II at low luminosity. As the Tevatron instantaneous luminosity increases, the limitation due to this simple algorithm starts to become clear. As a result, some of the most important jet and MET (missing ET) related triggers have large growth terms in cross section at higher luminosity. In this paper, we present an upgrade of the L2CAL system which makes the full calorimeter trigger tower information directly available to the level 2 decision CPU. This upgrade is based on the Pulsar, a general purpose VME board developed at CDF and already used for upgrading both the level 2 global decision crate and the level 2 silicon vertex tracking. The upgrade system allows more sophisticated algorithms to be implemented in software and both level 2 jets and MET can be made nearly equivalent to offline quality, thus significantly improving the performance and flexibility of the jet and MET related triggers. This is a natural expansion of the already-upgraded level 2 trigger system, and is a big step forward to improve the CDF triggering capability at level 2. This paper describes the design, the hardware and software implementation and the performance of the upgrade system.

Evidence for bso→ decay and measurements of branching ratio and ACP for B+→K+

We present the first evidence of charmless decays of the B(0)(s) meson, the decay B(0)(s)--> phiphi, and a measurement of the branching ratio BR(B(0)(s)--> phiphi) using 180 pb(-1) of data collected by the CDF II experiment at the Fermilab Tevatron collider. In addition, the BR and direct CP asymmetry for the B+-->phiK+ decay are measured. We obtain BR(B(0)(s)--> phiphi)=[14(+6)(-5)(stat)+/-6(syst)] x 10(-6), BR(B+-->phiK+)=[7.6+/-1.3(stat)+/-0.6(syst)] x 10(-6), and A(CP)(B+-->phiK+)= -0.07+/-0.17(stat)+0.03 / -0.02(syst). Both decays are governed in the standard model by second order (penguin) b-->s(-)ss amplitudes.