Engineering topics
Eigen, G
Publications and source records attributed to Eigen, G.
Search for CP Violation in the Decay D+/- to Ks pi+/-
We report on a search for CP violation in the decay D{sup {+-}} {yields} K{sub S}{sup 0}{pi}{sup {+-}} using a data set corresponding to an integrated luminosity of 469 fb{sup -1} collected with the BABAR detector at the PEP-II asymmetric energy e{sup +}e{sup -} storage rings. The CP-violating decay rate asymmetry A{sub CP} is determined to be (-0.44 {+-} 0.13(stat) {+-} 0.10(syst))%, consistent with zero at 2.7 {sigma} and with the standard model prediction of (-0.332 {+-} 0.006)%. This is currently the most precise measurement of this parameter.
Correlated Leading Baryon-antibaryon Production in e+e- to ccbar to Lambda_c+ antiLambda_c- X
We present a study of 649 {+-} 35 e{sup +}e{sup -} {yields} c{bar c} events produced at {radical}s {approx} 10.6 GeV containing both a {Lambda}{sub c}{sup +} baryon and a {bar {Lambda}}{sub c}{sup -} antibaryon. The number observed is roughly four times that expected if the leading charmed hadron types are uncorrelated, confirming an observation by the CLEO Collaboration. We find a 2-jet topology in these events but very few additional baryons, demonstrating that the primary c and {bar c} are predominantly contained in a correlated baryon-antibaryon system. In addition to the charmed baryons we observe on average 2.6 {+-} 0.2 charged intermediate mesons, predominantly pions, carrying 65% of the remaining energy.
Study of B to X \gamma Decays and Determination of |V_{td}/V_{ts}|
Using a sample of 471 million B{bar B} events collected with the BABAR detector, we study the sum of seven exclusive final states B {yields} X{sub s(d){gamma}}, where X{sub s(d)} is a strange (non-strange) hadronic system with a mass of up to 2.0 GeV/c{sup 2}. After correcting for unobserved decay modes, we obtain a branching fraction for b {yields} d{gamma} of (9.2 {+-} 2.0(stat.) {+-} 2.3(syst.)) x 10{sup -6} in this mass range, and a branching fraction for b {yields} s{gamma} of (23.0 {+-} 0.8(stat.) {+-} 3.0(syst.)) x 10{sup -5} in the same mass range. We find {Beta}(b{yields}d{gamma})/{Beta}(b{yields}s{gamma}) = 0.040 {+-} 0.009(stat.) {+-} 0.010(syst.), from which we determine |V{sub td}/V{sub ts}| = 0.199 {+-} 0.022(stat.) {+-} 0.024(syst.) {+-} 0.002(th.).
Measurement of the Mass and Width of the Ds1(2536)+ Meson
The decay width and mass of the D{sub s1}(2536){sup +} meson are measured via the decay channel D{sub s1}{sup +} {yields} D*{sup +} K{sub S}{sup 0} using 385 fb{sup -1} of data recorded with the BABAR detector in the vicinity of the {Upsilon}(4S) resonance at the PEP-II asymmetric-energy electron-positron collider. The result for the decay width is {Gamma}(D{sub s1}{sup +}) = 0.92 {+-} 0.03 (stat.) {+-} 0.04 (syst.)MeV. For the mass, a value of m(D{sub s1}{sup +}) = 2535.08 {+-} 0.01 (stat.) {+-} 0.15 (syst.)MeV/c{sup 2} is obtained. The mass difference between the D{sub s1}{sup +} and the D*{sup +} is measured to be m(D{sub s1}{sup +})-m(D*{sup +}) = 524.83 {+-} 0.01 (stat.) {+-} 0.04 (syst.)MeV/c{sup 2}, representing a significant improvement compared to the current world average. The unnatural spin-parity assignment for the D{sub s1}{sup +} meson is confirmed.
Cross Sections for the Reactions e+e to K+ K- pi+pi-, K+ K- pi0pi0, and K+ K- K+ K- Measured Using Initial-State Radiation
We study the processes e{sup +}e{sup -} {yields} K{sup +}K{sup -}{pi}{sup +}{pi}-{gamma}, K{sup +}K{sup -}{pi}{sup 0}{pi}{sup 0}{gamma}, and K{sup +}K{sup -}K{sup +}K{sup -}{gamma}, where the photon is radiated from the initial state. About 84000, 8000, and 4200 fully reconstructed events, respectively, are selected from 454 fb{sup -1} of BABAR data. The invariant mass of the hadronic final state defines the e{sup +}e{sup -} center-of-mass energy, so that the K{sup +}K{sup -}{pi}{sup +}{pi}{sup -}{gamma} data can be compared with direct measurements of the e{sup +}e{sup -} {yields} K{sup +}K{sup -}{pi}{sup +}{pi}{sup -} reaction. No direct measurements exist for the e{sup +}e{sup -} {yields} K{sup +}K{sup -}{pi}{sup 0}{pi}{sup 0} or e{sup +}e{sup -} {yields} K{sup +}K{sup -}K{sup +}K{sup -} reactions, and we present an update of our previous result with doubled statistics. Studying the structure of these events, we find contributions from a number of intermediate states, and extract their cross sections. In particular, we perform a more detailed study of the e{sup +}e{sup -} {yields} {phi}(1020){pi}{pi}{gamma} reaction, and confirm the presence of the Y (2175) resonance in the {phi}(1020)f{sub 0}(980) and K{sup +}K{sup -} f{sub 0}(980) modes. In the charmonium region, we observe the J/{psi} in all three final states and in several intermediate states, as well as the {phi}(2S) in some modes, and measure the corresponding branching fractions.
Evidence for Direct CP Violation in the Measurement of the Cabibbo-Kobayashi-Maskawa Angle gamma with B-+ to D(*) K(*)-+ Decays
We report the measurement of the Cabibbo-Kobayashi-Maskawa CP-violating angle {gamma} through a Dalitz plot analysis of neutral D meson decays to K{sub S}{sup 0}{pi}{sup +}{pi}{sup -} and K{sub S}{sup 0} K{sup +}K{sup -} produced in the processes B{sup {-+}} {yields} DK{sup {-+}}, B{sup {-+}} {yields} D* K{sup {-+}} with D* {yields} D{pi}{sup 0}, D{gamma}, and B{sup {-+}} {yields} DK*{sup {-+}} with K*{sup {-+}} {yields} K{sub S}{sup 0}{pi}{sup {-+}}, using 468 million B{bar B} pairs collected by the BABAR detector at the PEP-II asymmetric-energy e{sup +}e{sup -} collider at SLAC. We measure {gamma} = (68 {+-} 14 {+-} 4 {+-} 3){sup o} (modulo 180{sup o}), where the first error is statistical, the second is the experimental systematic uncertainty and the third reflects the uncertainty in the description of the neutral D decay amplitudes. This result is inconsistent with {gamma} = 0 (no direct CP violation) with a significance of 3.5 standard deviations.
Measurement of $D^0-overline{D}^0$ mixing parameters using $D^0 \to K_S^0 \pi^ \pi^-$ and $D^0 \to K_S^0 K^ K^-$ decays
We report a direct measurement of D{sup 0}-{bar D}{sup 0} mixing parameters through a time-dependent amplitude analysis of the Dalitz plots of D{sup 0} {yields} K{sub S}{sup 0}{pi}{sup +}{pi}{sup -} and, for the first time, D{sup 0} {yields} K{sub S}{sup 0}K{sup +}K{sup -} decays. The low-momentum pion {pi}{sub s}{sup +} in the decay D*{sup +} {yields} D{sup 0}{pi}{sub s}{sup +} identifies the flavor of the neutral D meson at its production. Using 468.5 fb{sup -1} of e{sup +}e{sup -} colliding-beam data recorded near {radical}s = 10.6 GeV by the BABAR detector at the PEP-II asymmetric-energy collider at SLAC, we measure the mixing parameters x = [1.6 {+-} 2.3 (stat.) {+-} 1.2 (syst.) {+-} 0.8 (model)] x 10{sup -3}, and y = [5.7 {+-} 2.0 (stat.) {+-} 1.3 (syst.) {+-} 0.7 (model)] x 10{sup -3}. These results provide the best measurement to date of x and y. The knowledge of the value of x, in particular, is crucial for understanding the origin of mixing.
Search for CP Violation using $T$-odd Correlations in $D^0 \to K^+ K^- \pi^+ \pi^-$ Decays
We search for CP violation in a sample of 4.7 x 10{sup 4} Cabibbo suppressed D{sup 0} {yields} K{sup +}K{sup -}{pi}{sup +}{pi}{sup -} decays. We use 470 fb{sup -1} of data recorded by the BABAR detector at the PEP-II asymmetric-energy e{sup +}e{sup -} storage rings running at center-of-mass energies near 10.6 GeV. CP violation is searched for in the difference between the T-odd asymmetries, obtained using triple product correlations, measured for D{sup 0} and {bar D}{sup 0} decays. The measured CP violation parameter is A{sub T} = (1.0 {+-} 5.1{sub stat} {+-} 4.4{sub syst}) x 10{sup -3}.
Search for Charged Lepton Violation in Narrow Upsilon Decays
Charged lepton flavor violating processes are unobservable in the standard model, but they are predicted to be enhanced in several extensions to the standard model, including supersymmetry and models with leptoquarks or compositeness. We present a search for such processes in a sample of 99 x 10{sup 6} {Upsilon}(2S) decays and 117 x 10{sup 6} {Upsilon}(3S) decays collected with the BABAR detector. We place upper limits on the branching fractions {Beta}({Upsilon}(nS) {yields} e{sup {+-}}{tau}{sup {-+}}) and {Beta}({Upsilon}(nS) {yields} {mu}{sup {+-}}{tau}{sup {-+}}) (n = 2, 3) at the 10{sup -6} level and use these results to place lower limits of order 1 TeV on the mass scale of charged lepton flavor violating effective operators.
Measurements of Branching Fractions and CP Asymmetries and Studies of Angular Distributions for B to phi phi K Decays
We present branching fraction and CP asymmetry measurements as well as angular studies of B {yields} {phi}{phi}K decays using 464 x 10{sup 6} B{bar B} events collected by the BABAR experiment. The branching fractions are measured in the {phi}{phi} invariant mass range below the {eta}{sub c} resonance (m{sub {phi}{phi}} < 2.85 GeV). We find {Beta}(B{sup +} {yields} {phi}{phi}K{sup +}) = (5.6 {+-} 0.5 {+-} 0.3) x 10{sup -6} and {Beta}(B{sup 0} {yields} {phi}{phi}K{sup 0}) = (4.5 {+-} 0.8 {+-} 0.3) x 10{sup -6}, where the first uncertaintiy is statistical and the second systematic. The measured direct CP asymmetries for the B{sup {+-}} decays are A{sub CP} = -0.10 {+-} 0.08 {+-} 0.02 below the {eta}{sub c} threshold (m{sub {phi}{phi}} < 2.85 GeV) and A{sub CP} = 0.09 {+-} 0.10 {+-} 0.02 in the {eta}{sub c} resonance region (m{sub {phi}{phi}} in [2.94,3.02] GeV). Angular distributions are consistent with J{sub P} = 0{sup -} in the {eta}{sub c} resonance region and favor J{sup P} = 0{sup +} below the {eta}{sub c} resonance.
Measurement of Partial Branching Fractions of Inclusive Charmless B Meson Decays to K , K0, and pi
The authors present measurements of partial branching fractions of B {yields} K{sup +}X, B {yields} K{sup 0} X, and B {yields} {pi}{sup +}X, where X denotes any accessible final state above the endpoint for B decays to charmed mesons, specifically for momenta of the candidate hadron greater than 2.34 (2.36) GeV for kaons (pions) in the B rest frame. These measurements are sensitive to potential new-phisics particles which could enter the b {yields} s(d) loop transitions. The analysis is performed on a data sample consisting of 383 x 10{sup 6} B{bar B} pairs collected with the BABAR detector at the PEP-II e{sup +}e{sup -} asymmetric energy collider. The results are in agreement with standard model predictions and exclude large enhancements of the inclusive branching fraction due to sources of new physics.
Measurements of branching fractions, polarizations, and direct CP-violation asymmetries in B -> rho0 K* and B -> f0(980) K* decays
We present measurements of the branching fractions, longitudinal polarization, and direct CP-violation asymmetries for the decays B{sup +} {yields} {rho}{sup 0}K*{sup +} and B{sup +} f{sub 0}(980)K*{sup +} with a sample of (467 {+-} 5) x 10{sup 6} B{bar B} pairs collected with the BABAR detector at the PEP-II asymmetric-energy e{sup +}e{sup -} collider at the SLAC National Accelerator Laboratory. We observe B{sup +} {yields} {rho}{sup 0}K*{sup +} with a significance of 5.3{sigma} and measure the branching fraction {Beta}(B{sup +} {yields} {rho}{sup 0}K*{sup +}) = (4.6 {+-} 1.0 {+-} 0.4) x 10{sup -6}, the longitudinal polarization f{sub L} = 0.78 {+-} 0.12 {+-} 0.03, and the CP-violation asymmetry A{sub CP} = 0.31 {+-} 0.13 {+-} 0.03. We observe B{sup +} {yields} f{sub 0}(980)K*{sup +} and measure the branching fraction {Beta}(B{sup +} {yields} f{sub 0}(980)K*{sup +}) x {Beta}(f{sub 0}(980) {yields} {pi}{sup +}{pi}{sup -}) = (4.2 {+-} 0.6 {+-} 0.3) x 10{sup -6} and the CP-violation asymmetry A{sub CP} = -0.15 {+-} 0.12 {+-} 0.03. The first uncertainty quoted is statistical and the second is systematic.
Analysis of the D+ --> K- pi+ e+ nu_e decay channel
Using 347.5 fb{sup -1} of data recorded by the BABAR detector at the PEP-II electron-positron collider, 244 x 10{sup 3} signal events for the D{sup +} {yields} K{sup -}{pi}{sup +}e{sup +}{nu}{sub e} decay channel are analyzed. This decay mode is dominated by the {bar K}*(892){sup 0} contribution. We determine the {bar K}*(892){sup 0} parameters: m{sub K*(892){sup 0}} = (895.4{+-}0.2{+-}0.2) MeV/c{sup 2}, {Lambda}{sub K*(892){sup 0}}{sup 0} = (46.5{+-}0.3{+-}0.2) MeV/c{sup 2} and the Blatt-Weisskopf parameter r{sub BW} = 2.1{+-}0.5{+-}0.5 (GeV/c){sup -1} where the first uncertainty comes from statistics and the second from systematic uncertainties. We also measure the parameters defining the corresponding hadronic form factors at q{sup 2} = 0 (r{sub V} = V(0)/A{sub 1}(0) = 1.463{+-}0.017{+-}0.031, r{sup 2} = A{sub 2}(0)/A{sub 1}(0) = 0.801{+-}0.020{+-}0.020) and the value of the axial-vector pole mass parameterizing the q{sup 2} variation of A{sub 1} and A{sub 2}: m{sub A} = (2.63{+-}0.10{+-}0.13) GeV/c{sup 2}. The S-wave fraction is equal to (5.79{+-}0.16{+-}0.15)%. Other signal components correspond to fractions below 1%. Using the D{sup +} {yields} K{sup -}{pi}{sup +}{pi}{sup +} channel as a normalization, we measure the D{sup +} semileptonic branching fraction: {Beta}(D{sup +} {yields} K{sup -}{pi}{sup +}e{sup +}{nu}{sub e}) = (4.00 {+-} 0.03 {+-} 0.04 {+-} 0.09) x 10{sup -2} where the third uncertainty comes from external inputs. We then obtain the value of the hadronic form factor A{sub 1} at q{sup 2} = 0: A{sub 1}(0) = 0.6200 {+-} 0.0056 {+-} 0.0065 {+-} 0.0071. Fixing the P-wave parameters we measure the phase of the S-wave for several values of the K{pi} mass. These results confirm those obtained with K{pi} production at small momentum transfer in fixed target experiments.
Search for b --> u Transitions in B^{+-} --> [K^{-+} pi^{+-} pi0]_D K^{+-} Decays
The authors present a study of the decays B{sup {+-}} {yields} DK{sup {+-}} with D mesons reconstructed in the K{sup +}{pi}{sup -}{pi}{sup 0} or K{sup -}{pi}{sup +}{pi}{sup 0} final states, where D indicates a D{sup 0} or a {bar D}{sup 0} meson. Using a sample of 474 million B{bar B} pairs collected with the BABAR detector at the PEP-II asymmetric-energy e{sup +}e{sup -} collider at SLAC, they measure the ratios R{sup {+-}} {triple_bond} {Lambda}(B{sup {+-}}{yields}[K{sup {-+}}{pi}{sup {+-}}{pi}{sup 0}]{sub D}K{sup {+-}})/{Lambda}(B{sup {+-}}{yields}[K{sup {+-}}{pi}{sup {-+}}{pi}{sup 0}]{sub D}K{sup {+-}}). They obtain R{sup +} = (5{sub -10}{sup +12}(stat){sub -4}{sup +2}(syst)) x 10{sup -3} and R{sup -} = (12{sub -10}{sup +12}(stat){sub -5}{sup +3}(syst)) x 10{sup -3}, from which they extract the upper limits at 90% probability: R{sup +} < 23 x 10{sup -3} and R{sup -} < 29 x 10{sup -3}. Using these measurements, they obtain an upper limit for the ratio r{sub B} of the magnitudes of the b {yields} u and b {yields} c amplitudes r{sub B} < 0.13 at 90% probability.
Measurement of the branching fraction for $\tau\to\eta K\nu_\tau$ and a search for second-class currents in $\tau\to\eta\pi\nu_\tau$ with $\eta\to\pi^ \pi^-\pi0$
The authors report on analyses of tau lepton decays {tau}{sup -} {yields} {eta}K{sup -}{nu}{sub {tau}} and {tau}{sup -} {yields} {eta}{pi}{sup -}{nu}{sub {tau}}, with {eta} {yields} {pi}{sup +}{pi}{sup -}{pi}{sup 0}, using 470 fb{sup -1} of data from the BABAR experiment at PEP-II, collected at center-of-mass energies at and near the {Upsilon}(4S) resonance. They measure the branching fraction for the {tau}{sup -} {yields} {eta}K{sup -}{nu}{sub {tau}} decay mode, {Beta}({tau}{sup -} {yields} {eta}K{sup -}{nu}{sub {tau}}) = (1.42 {+-} 0.11(stat) {+-} 0.07(syst)) x 10{sup -4}, and report a 95% confidence level upper limit for the second-class current process {tau}{sup -} {yields} {eta}{pi}{sup -}{nu}{sub {tau}}, {Beta}({tau}{sup -} {yields} {eta}{pi}{sup -}{nu}{sub {tau}}) < 9.9 x 10{sup -5}.
Measurement of the B0 ->π−ℓνand B ->η(′)ℓνBranching Fractions, the B0 ->π−ℓνand B ->ηℓνForm-Factor Shapes, and Determination of |Vub|
We report the results of a study of the exclusive charmless semileptonic decays, B{sup +} {yields} {eta}{sup {prime}}{ell}{sup +}{nu} and B{sup 0} {yields} {pi}{sup -}{ell}{sup +}{nu}, undertaken with approximately 464 million B{bar B} pairs collected at the {Upsilon}(4S) resonance with the BABAR detector. The analysis uses events in which the signal B decays are reconstructed with a loose neutrino reconstruction technique. We obtain partial branching fractions for B{sup +} {yields} {eta}{ell}{sup +}{nu} and B{sup 0} {yields} {pi}{sup -}{ell}{sup +}{nu} decays in three and 12 bins of q{sup 2}, respectively, from which we extract the f{sub +}(q{sup 2}) form-factor shapes and the total branching fractions {Beta}(B{sup +} {yields} {eta}{ell}{sup +}{nu}) = (0.36 {+-} 0.05{sub stat} {+-} 0.04{sub syst}) x 10{sup -4} and {Beta}(B{sup 0} {yields} {pi}{sup -}{ell}{sup +}{nu}) = (1.42 {+-} 0.05{sub stat} {+-} 0.07{sub syst}) x 10{sup -4}. We also measure {Beta}(B{sup +} {yields} {eta}{sup {prime}}{ell}{sup +}{nu}) = (0.24 {+-} 0.08{sub stat} {+-} 0.03{sub syst}) x 10{sup -4}. We obtain values for the magnitude of the CKM matrix element |V{sub ub}| using three different QCD calculations.
Evidence for B+ --> tau+ nu_tau Decays using Hadronic B Tags
We present a search for the decay B{sup +} --> {tau}{sup +} {nu}{sub {tau}} using 467.8 x 10{sup 6} B{anti B} pairs collected at the {Upsilon}(4S) resonance with the BABAR detector at the SLAC PEP-II B-Factory. We select a sample of events with on completely reconstructed B{sup -} in an hadronic decay mode (B{sup -} --> D{sup (*)0}X{sup -} and B{sup -} --> J/{psi} X{sup -}). We examine the rest of the event to search for a B{sup +} --> {tau}{sup +} {nu}{sub {tau}} decay. We identify the {tau}{sup +} lepton in the following modes: {tau}{sup +} --> e{sup +} {nu}{sub e}{anti {nu}}{sub {tau}}, {tau}{sup +} --> {mu}{sup +} {nu}{sub {mu}}{anti {nu}}{sub {tau}}, {tau}{sup +} --> {pi}{sup +}{anti {nu}}{sub {tau}} and {tau}{sup +} --> {rho}{anti {nu}}{sub {tau}}. We find an excess of events with respect to expected background, which excludes the null signal hypothesis at the level of 3.3 {sigma} and can be converted to a branching fraction central value of B(B{sup +} --> {tau}{sup +} {nu}{sub {tau}})= (1.80{sup + 0.57}{sub - 0.54}(stat.) {+-} 0.26 (syst.)) x 10{sup -4}.