Luminosity Upgrades For The Slc

Recent performance improvements at the SLAC Linear Collider (SLC) have led to a proposal to further increase the luminosity up to a factor of four through a series of modest hardware upgrades. New final focus optics introduced in 1997 combined with permanent magnet octupoles have reduced the contribution to the final beam size due to higher order aberrations. The minimum betas achievable at the IP are presently limited by the increase in detector backgrounds as the beam is focused more strongly. By moving the final quadrupoles closer to the interaction point (IP), one can reduce the synchrotron radiation background while decreasing the IP betas. Other upgrades include increasing the bending radius in the final focus to minimize emittance dilutions due to synchrotron radiation, a fast feedforward from the linac to the final focus to cancel trajectory jitter, and a change in the horizontal damping ring partition number to reduce the emittance of the extracted beam. With these upgrades, t..

Search for radiative b-hadron decays in p(p)over-bar collisions at root s=1.8 TeV RID C-1693-2008 RID A-5169-2010 RID E-4473-2011 RID C-2406-2008

We have performed a search for radiative b-hadron decays using events produced in p (p) over bar collisions at roots=1.8 TeV and collected by the Collider Detector at Fermilab. The decays we considered were (B) over bar (0)(d)-->(K) over bar*(0)(-->K(-)pi(+))gamma, (B) over bar (0)(s)-->phi(-->K+K-)gamma, Lambda(b)(0)-->Lambda(-->ppi(-))gamma, and their charge conjugates. Two independent methods to identify photons from such decays were employed. In the first method, the photon was detected in the electromagnetic calorimeter. In the second method, the photon was identified by an electron-positron pair produced through the external photon conversion before the tracking detector volume. By combining the two methods we obtain upper limits on the branching fractions for the (B) over bar (0)(d), (B) over bar (0)(s), and Lambda(b)(0) radiative decays which, at the 95% confidence level, are found to be B((B) over bar (0)(d)-->(K) over bar*(0)gamma)phigamma)Lambdagamma)<1.9x10(-3)

First measurement of the ratio B(t -> Wb)/B(t -> Wq) and associated limit on the Cabibbo-Kobayashi-Maskawa element vertical bar V-tb vertical bar RID C-1693-2008 RID A-5169-2010

We present the first measurement of the ratio of branching fractions R equivalent to B(t --> Wb)/B(t --> Wq) from pa collisions at roots = 1.8 TeV. The data set corresponds to 109 pb(-1) of data recorded by the Collider Detector at Fermilab during the 1992-95 Tevatron run. We measure R = 0.94(-0.24)(+0.31)(stat + syst) or R > 0.61 (0.56) at 90% (95)% C.L., in agreement with the standard model predictions. This measurement yields a limit on the Cabibbo-Kobayashi-Maskawa quark mixing matrix element \V-tb\ under the assumption of three generations and unitarity

Measurement of CP-Violating Asymmetries in B0 Decays to CP Eigenstates

We present measurements of time-dependent CP-violating asymmetries in neutral B decays to several CP eigenstates. The measurement uses a data sample of 23×10^6 ϒ(4S)→BB̅ decays collected by the BABAR detector at the PEP-II asymmetric B Factory at SLAC. In this sample, we find events in which one neutral B meson is fully reconstructed in a CP eigenstate containing charmonium and the flavor of the other neutral B meson is determined from its decay products. The amplitude of the CP-violating asymmetry, which in the standard model is proportional to sin2β, is derived from the decay time distributions in such events. The result is sin2β = 0.34±0.20(stat)±0.05(syst)

Observation of CP violation in the B0 meson system

We present an updated measurement of time-dependent CP-violating asymmetries in neutral B decays with the BABAR detector at the PEP-II asymmetric B Factory at SLAC. This result uses an additional sample of Upsilon(4S) decays collected in 2001, bringing the data available to 32 million B-anti-B pairs. We select events in which one neutral B meson is fully reconstructed in a final state containing charmonium and the flavor of the other neutral B meson is determined from its decay products. The amplitude of the CP-violating asymmetry, which in the Standard Model is proportional to sin2beta, is derived from the decay time distributions in such events. The result sin2beta = 0.59 +/- 0.14 (stat) +/- 0.05 (syst) establishes CP violation in the B^0 meson system. We also determine |lambda| = 0.93 +/- 0.09 {stat} +/- 0.03 {syst}, consistent with no direct CP violation.Comment: 8 pages, 2 figures, submitted to Physical Review Letter

The BaBar detector

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Measurement of B-0 -> D-s(*)D+*(-) branching fractions and B-0 -> D-s*D+*(-) polarization with a partial reconstruction technique RID C-2728-2008 RID C-5223-2009 RID C-5719-2008 RID D-1055-2009 RID A-2675-2009

We present a study of the decays B-0 --> D-s((*)) D*-, using 20.8 fb(-1) of e(+)e(-) annihilation data recorded with the BABAR detector. The analysis is conducted with a partial reconstruction technique, in which only the D-s((*)+) and the soft pion from the D*- decay are reconstructed. We measure the branching fractions B(B-0 --> Ds+D*-) = (1.03 +/- 0.14 +/- 0.13 +/- 0.26)% and B(B-0 --> D-s(*+) D*-) = (1.97 +/- 0.15 +/- 0.30+/- 0.49)%, where the first error is statistical, the second is systematic, and the third is the error due to the D-s(+) --> phipi(+) branching fraction uncertainty. From the B-0 --> D-s(*+) D*- angular distributions, we measure the fraction of longitudinal polarization Gamma(L)/Gamma = (51.9 +/- 5.0 +/- 2.8)%, which is consistent with theoretical predictions based on factorization

Simultaneous measurement of the B-0 meson lifetime and mixing frequency with B-0 -> D(*-)l(+)nu(l) decays RID C-2728-2008 RID C-5223-2009 RID C-5719-2008 RID D-1055-2009 RID A-2675-2009

We measure the B-0 lifetime tau(B)(0) and the B-0-(B) over bar (0) oscillation frequency Deltam(d) with a sample of approximately 14000 exclusively reconstructed B-0-->D(*-)l(+)nul signal events, selected from 23 million B (B) over bar pairs recorded at the Y(4S) resonance with the BABAR detector at the Stanford Linear Accelerator Center. The decay position of the other B is determined with the remaining tracks in the event, and its b-quark flavor at the time of decay is determined with a tagging algorithm that exploits the correlation between the flavor of the b quark and the charges of its decay products. The lifetime and oscillation frequencies are measured simultaneously with an unbinned maximum-likelihood fit that uses, for each event, the measured difference in decay times of the two B mesons (Deltat), the calculated uncertainty on Deltat, the signal and background probabilities, and b-quark tagging information for the other B. The results are tau(B)(0)=(1.523(-0.023)(+0.024)+/-0.022) ps and Deltam(d)=(0.492+/-0.018+/-0.013) ps(-1). The statistical correlation coefficient between tau(B)(0) and Deltam(d) is -0.22

Measurement of time-dependent CP asymmetries and the CP-odd fraction in the decay B-0 -> D*+D*- RID C-2728-2008 RID C-5223-2009 RID C-5719-2008 RID D-1055-2009 RID A-2675-2009

We present a measurement of time-dependent CP asymmetries and an updated determination of the CP-odd fraction in the decay B-0-->D*+D*- using a data sample of 88x10(6)B (B) over bar pairs collected by the BABAR detector at the PEP-II B Factory at SLAC. We determine the CP-odd fraction to be 0.063+/-0.055(stat)+/-0.009(syst). The time-dependent CP asymmetry parameters Im(lambda(+)) and \lambda(+)\ are determined to be 0.05+/-0.29(stat)+/-0.10(syst) and 0.75+/-0.19(stat)+/-0.02(syst), respectively. The standard model predicts these parameters to be -sin2beta and 1, respectively, in the absence of penguin diagram contributions