I. Furic

Boosted Decision Trees in the Level-1 Muon Endcap Trigger at CMS

The first implementation of a Machine Learning Algorithm inside a Level-1 trigger system at the LHC is presented. The Endcap Muon Track Finder (EMTF) at CMS uses Boosted Decision Trees (BDTs) to infer the momentum of muons in the forward region of the detector, based on 25 different variables. Combinations of these variables representing 2 distinct patterns are evaluated offline using regression BDTs. The predictions for the 2 input variable combinations are stored in a 1.2 GB look-up table in the EMTF hardware. The BDTs take advantage of complex correlations between variables, the inhomogeneous magnetic field, and non-linear effects – like inelastic scattering – to distinguish high momentum signal muons from the overwhelming low-momentum background. The new momentum algorithm reduced the background rate by a factor of three with respect to the previous analytic algorithm, with further improvements foreseen in the coming year.

Boosted Decision Trees in the CMS Level-1 Endcap Muon Trigger

The first implementation of Boosted Decision Trees (BDTs) inside a Level-1 trigger system at the LHC is presented. The Endcap Muon Track Finder (EMTF) at CMS uses BDTs to infer the momentum of muons in the forward region of the detector, based on 25 different variables. Combinations of these variables are evaluated offline using regression BDTs, whose output is stored in 1.2 GB look-up tables (LUTs) in the EMTF hardware. These BDTs take advantage of complex correlations between variables, the inhomogeneous magnetic field, and non-linear effects such as inelastic scattering to distinguish high-momentum signal muons from the overwhelming low-momentum background. The LUTs are used to turn the complex BDT evaluation into a simple look-up operation in fixed low latency. The new momentum assignment algorithm has reduced the trigger rate by a factor of 3 at the 25 GeV trigger threshold with respect to the legacy system, with further improvements foreseen in the coming year.

Measurement of the ratio of branching fractions B(B{sup {+-}}{yields}J/{psi}{pi}{sup {+-}})/B(B{sup {+-}}{yields}J/{psi}K{sup {+-}})

We report a measurement of the ratio of branching fractions of the decays B{sup {+-}}{yields}J/{psi}{pi}{sup {+-}} and B{sup {+-}}{yields}J/{psi}K{sup {+-}} using the CDF II detector at the Fermilab Tevatron Collider. The signal from the Cabbibo-suppressed B{sup {+-}}{yields}J/{psi}{pi}{sup {+-}} decay is separated from B{sup {+-}}{yields}J/{psi}K{sup {+-}} using the B{sup {+-}}{yields}J/{psi}K{sup {+-}} invariant mass distribution and the kinematical differences of the hadron track in the two decay modes. From a sample of 220 pb{sup -1} of pp collisions at {radical}(s)=1.96 TeV, we observe 91{+-}15 B{sup {+-}}{yields}J/{psi}{pi}{sup {+-}} events together with 1883{+-}34 B{sup {+-}}{yields}J/{psi}K{sup {+-}} events. The ratio of branching fractions is found to be B(B{sup {+-}}{yields}J/{psi}{pi}{sup {+-}})/B(B{sup {+-}}{yields}J/{psi}K{sup {+-}})=(4.86{+-}0.82(stat){+-}0.15(syst))%.

Measurement of {sigma}{sub {lambda}{sub b}{sup 0}}/{sigma}{sub B{sup 0}}xB({lambda}{sub b}{sup 0}{yields}{lambda}{sub c}{sup +}{pi}{sup -})/B(B{sup =} 0{yields}D{sup +}{pi}{sup -}) in pp Collisions at {radical}(s)=1.96 TeV

We present the first observation of the baryon decay {lambda}{sub b}{sup 0}{yields}{lambda}{sub c}{sup +}{pi}{sup -} followed by {lambda}{sub c}{sup +}{yields}pK{sup -}{pi}{sup +} in 106 pb{sup -1} pp collisions at {radical}(s)=1.96 TeV in the CDF experiment. In order to reduce systematic error, the measured rate for {lambda}{sub b}{sup 0} decay is normalized to the kinematically similar meson decay B{sup 0}{yields}D{sup +}{pi}{sup -} followed by D{sup +}{yields}{pi}{sup +}K{sup -}{pi}{sup +}. We report the ratio of production cross sections ({sigma}) times the ratio of branching fractions (B) for the momentum region integrated above p{sub T}>6 GeV/c and pseudorapidity range |{eta}|<1.3: {sigma}(pp{yields}{lambda}{sub b}{sup 0}X)/{sigma}(pp{yields}B{sup 0}X)xB({lambda}{sub b}{sup 0}{yields}{lambda}{sub c}{sup =} +{pi}{sup -})/B(B{sup 0}{yields}D{sup +}{pi}{sup -})=0.82{+-} 0.08(stat){+-}0.11(syst){+-}0.22[B({lambda}{sub c}{sup +}{yields}pK{sup -}{pi}{sup +})].

Polarizations of J/{psi} and {psi}(2S) Mesons Produced in pp Collisions at {radical}(s)=1.96 TeV

We have measured the polarizations of J/psi and psi(2S) mesons as functions of their transverse momentum p(T) when they are produced promptly in the rapidity range |y| < 0.6 with p(T) > or =5 GeV/c. The analysis is performed using a data sample with an integrated luminosity of about 800 pb(-1) collected by the CDF II detector. For both vector mesons, we find that the polarizations become increasingly longitudinal as p(T) increases from 5 to 30 GeV/c. These results are compared to the predictions of nonrelativistic quantum chromodynamics and other contemporary models. The effective polarizations of J/psi and psi(2S) mesons from B-hadron decays are also reported.

Measurement of the Ratios of Branching Fractions B(B{sub s}{sup 0}{yields}D{sub s}{sup -}{pi}{sup +}{pi}{sup +}{pi}{sup -})/B(B{sup 0}{yields}D{sup -}{pi}{sup +}{pi}{sup +}{pi}{sup -}) and B(B{sub s}{sup 0}{yields}D{sub s}{sup -}{pi}{sup +})/B(B{sup 0}{yields}D{sup -}{pi}{sup +})

Using 355 pb;{-1} of data collected by the CDF II detector in pp[over ] collisions at sqrt[s]=1.96 TeV at the Fermilab Tevatron, we study the fully reconstructed hadronic decays B_{(s)};{0}-->D_{(s)};{-}pi;{+} and B_{(s)};{0}-->D_{(s)};{-}pi;{+}pi;{+}pi;{-}. We present the first measurement of the ratio of branching fractions B(B_{s};{0}-->D_{s};{-}pi;{+}pi;{+}pi;{-})/B(B;{0}-->D;{-}pi;{+}pi;{+}pi;{-})=1.05+/-0.10(stat)+/-0.22(syst). We also update our measurement of B(B_{s};{0}-->D_{s};{-}pi;{+})/B(B;{0}-->D;{-}pi;{+}) to 1.13+/-0.08(stat)+/-0.23(syst), improving the statistical uncertainty by more than a factor of 2. We find B(B_{s};{0}-->D_{s};{-}pi;{+})=[3.8+/-0.3(stat)+/-1.3(syst)]x10;{-3} and B(B_{s};{0}-->D_{s};{-}pi;{+}pi;{+}pi;{-})=[8.4+/-0.8(stat)+/-3.2(syst)]x10;{-3}.Using 355 pb{sup -1} of data collected by the CDF II detector in pp collisions at {radical}(s)=1.96 TeV at the Fermilab Tevatron, we study the fully reconstructed hadronic decays B{sub (s)}{sup 0}{yields}D{sub (s)}{sup -}{pi}{sup +} and B{sub (s)}{sup 0}{yields}D{sub (s)}{sup -}{pi}{sup +}{pi}{sup +}{pi}{sup -}. We present the first measurement of the ratio of branching fractions B(B{sub s}{sup 0}{yields}D{sub s}{sup -}{pi}{sup +}{pi}{sup +}{pi}{sup -})/B(B{sup 0}{yields}D{sup -}{pi}{sup +}{pi}{sup +}{pi}{sup -})=1.05{+-}0.10(stat){+-}0.22(syst). We also update our measurement of B(B{sub s}{sup 0}{yields}D{sub s}{sup -}{pi}{sup +})/B(B{sup 0}{yields}D{sup -}{pi}{sup +}) to 1.13{+-}0.08(stat){+-}0.23(syst), improving the statistical uncertainty by more than a factor of 2. We find B(B{sub s}{sup 0}{yields}D{sub s}{sup -}{pi}{sup +})=[3.8{+-}0.3(stat){+-}1.3(syst)]x10{sup -3} and B(B{sub s}{sup 0}{yields}D{sub s}{sup -}{pi}{sup +}{pi}{sup +}{pi}{sup -})=[8.4{+-}0.8(stat){+-}3.2(syst)]x10{sup -3}.

Search for new physics in lepton+photon+X events with 929 pb{sup -1} of pp collisions at {radical}(s)=1.96 TeV

We present results of a search at CDF in 929±56pb-1 of pp collisions at 1.96 TeV for the anomalous production of events containing a high-transverse momentum charged lepton (l, either e or μ) and photon (γ), accompanied by missing transverse energy (E T), and/or additional leptons and photons, and jets (X). We use the same selection criteria as in a previous CDF Run I search, but with an order-magnitude larger data set, a higher pp collision energy, and the CDF II detector. We find 163 lγE T+X events, compared to an expectation of 150.6±13.0 events. We observe 74 lγ+X events, compared to an expectation of 65.1±7.7 events. We find no events similar to the Run I eeγγE T event.

Measurement of the B{sup +} production cross section in pp collisions at {radical}(s)=1960 GeV

We present a new measurement of the B{sup +} meson differential cross section d{sigma}/dp{sub T} at {radical}(s)=1960 GeV. The data correspond to an integrated luminosity of 739 pb{sup -1} collected with the upgraded CDF detector (CDF II) at the Fermilab Tevatron collider. B{sup +} candidates are reconstructed through the decay B{sup +}{yields}J/{psi}K{sup +}, with J/{psi}{yields}{mu}{sup +}{mu}{sup -}. The integrated cross section for producing B{sup +} mesons with p{sub T}{>=}6 GeV/c and |y|{<=}1 is measured to be 2.78{+-}0.24 {mu}b.

Measurement of {sigma}(pp{yields}Z){center_dot}B(Z{yields}{tau}{tau}) in pp collisions at {radical}(s)=1.96 TeV

We present a measurement of the inclusive production cross section for Z bosons decaying to tau leptons in p (p) over bar collisions at root s=1.96 TeV. We use a channel with one hadronically-decaying and one electronically-decaying tau. This measurement is based on 350 pb(-1) of CDF Run II data. Using a sample of 504 opposite sign e tau events with a total expected background of 190 events, we obtain sigma(p (p) over bar -> 4Z)center dot B(Z ->tau tau)=264 +/- 23(stat)+/- 14(syst)+/- 15(lumi) pb, in agreement with the next-to-next-to-leading order QCD prediction. This is the first CDF cross section measurement using hadronically-decaying taus in Run II.We present a measurement of the inclusive production cross section for Z bosons decaying to tau leptons in pp collisions at s=1.96TeV. We use a channel with one hadronically-decaying and one electronically-decaying tau. This measurement is based on 350pb-1 of CDF Run II data. Using a sample of 504 opposite sign eτ events with a total expected background of 190 events, we obtain σ(pp→4Z)•B(Z→ττ)=264±23(stat) ±14(syst)±15(lumi)pb, in agreement with the next-to-next-to- leading order QCD prediction. This is the first CDF cross section measurement using hadronically-decaying taus in Run II.

Search for {lambda}{sub b}{sup 0}{yields}p{pi} and {lambda}{sub b}{sup 0}{yields}pK decays in pp collisions at {radical}(s)=1.96 TeV

We report on a search for {lambda}{sub b}{sup 0}{yields}p{pi}{sup -} and {lambda}{sub b}{sup 0}{yields}pK{sup -} (and charge conjugate) decays in pp collisions at {radical}(s)=1.96 TeV using 193 pb{sup -1} of data collected by the CDF II experiment at the Fermilab Tevatron Collider. Data were collected using a track trigger that has been optimized to select tracks belonging to a secondary vertex that is typical of two-body charmless decays of b-flavored hadrons, including {lambda}{sub b}{sup 0} baryons. As no {lambda}{sub b}{sup 0} signal was observed, we set the upper limits on the branching fraction B({lambda}{sub b}{sup 0}{yields}ph{sup -}), where h is K or {pi}, of 2.3x10{sup -5} at 90% C.L. and 2.9x10{sup -5} at 95% C.L.We report on a search for Lambda_b -> p pi- and Lambda_b -> p K- (and charge conjugate) decays in p-pbar collisions at sqrt(s) = 1.96 TeV using 193 pb-1 of data collected by CDFII experiment at the Fermilab Tevatron Collider. Data were collected using a track trigger that has been optimized to select tracks belonging to a secondary vertex that is typical of two body charmless decays of b-flavored hadrons, including Lambda_b baryons. As no Lambda_b signal was observed, we set the upper limits on the branching fractions BR(Lambda_b -> p h-) where h is K or pi, of 2.3x10-5 at 90% C.L. and 2.9x10-5 at 95% C.L.