Search

We report a measurement of the production ratio of charged and neutral B mesons from ${\rm Y}\mathrm{}\left(4S\right)\mathrm{}$ decays based on the ratio of efficiency-corrected yields for the charmonium modes $J/\psi K^{+}$ and $J/\psi K_s^0$ with 81.9 ${\mathrm{fb}}^{\mathrm{-}1}$ of data collected with the BABAR detector on the ${\rm Y}\mathrm{}\left(4S\right)\mathrm{}$ resonance at 10.580 GeV. We find a value of $1.006\pm 0.036\left(\mathrm{stat}\right)\pm 0.031\left(\mathrm{syst}\right)$ for the ratio $R^{+/0\mathrm{}}=\Gamma \left({\rm Y}\mathrm{}\right(4S)\mathrm{}\to B^{+}{B}^{-})/\Gamma \left({\rm Y}\mathrm{}\right(4S)\mathrm{}\to B^0{B}^0).$

We present measurements of branching fractions of $B^0$ decays to multibody final states containing protons, based on $232\times {10}^6$ ${\rm Y}(4S)\to B\overline{B}$ decays collected with the BABAR detector at the SLAC PEP-II asymmetric-energy $B$ factory. We measure the branching fractions $\mathcal{B}(B^0\to {\overline{D}}^{0}p\overline{p})=(1.13\pm 0.06\pm 0.08)\times {10}^{-4}$, $\mathcal{B}(B^0\to {\overline{D}}^{*0}p\overline{p})=(1.01\pm 0.10\pm 0.09)\times {10}^{-4}$, $\mathcal{B}(B^0\to D^{-}p\overline{p}{\pi }^{+})=(3.38\pm 0.14\pm 0.29)\times {10}^{-4}$, and $\mathcal{B}(B^0\to D^{*-}p\overline{p}{\pi }^{+})=(4.81\pm 0.22\pm 0.44)\times {10}^{-4}$ where the first error is statistical and the second systematic. We present a search for the charmed pentaquark state, ${\Theta }_c(3100)$ observed by H1 and put limits on the branching fraction $\mathcal{B}(B^0\to {\Theta }_c\overline{p}{\pi }^{+})\times \mathcal{B}({\Theta }_c\to D^{*-}p)<14\times {10}^{-6}$ and $\mathcal{B}(B^0\to {\Theta }_c\overline{p}{\pi }^{+})\times \mathcal{B}({\Theta }_c\to D^{-}p)<9\times {10}^{-6}$. Upon investigation of the decay structure of the above four $B^0$ decay modes, we see an enhancement at low $p\overline{p}$ mass and deviations from phase-space in the $\overline{D}\overline{p}$ and $\overline{D}p$ invariant mass spectra.

Using a sample of $232\times {10}^6{\rm Y}(4S)\to B\overline{B}$ events collected with the BABAR detector at the PEP-II $B$ factory we study the decay $B^{-}\to [K^{+}{\pi }^{-}{]}_D{K}^{*-}$ where the $K^{+}{\pi }^{-}$ is either from a Cabibbo-favored ${\overline{D}}^0$ decay or doubly-suppressed $D^0$ decay. We measure two observables that are sensitive to the Cabibbo-Kobayashi-Maskawa angle $\gamma$; the ratio $R$ of the charge-averaged branching fractions for the suppressed and favored decays; and the charge asymmetry $A$ of the suppressed decays: $R=0.046\pm 0.031(\mathrm{stat})\pm 0.008(\mathrm{syst})$, $A=-0.22\pm 0.61(\mathrm{stat})\pm 0.17(\mathrm{syst})$.

A search for the decay of the $\tau$ lepton to five charged and two neutral pions is performed using data collected by the BABAR detector at the PEP-II asymmetric-energy $e^{+}{e}^{-}$ collider. The analysis uses $232{\mathrm{fb}}^{-1}$ of data at center-of-mass energies on or near the ${\rm Y}(4S)$ resonance. We observe 10 events with an expected background of ${6.5}_{-1.4}^{+2.0}$ events. In the absence of a signal, we set the limit on the branching ratio $\mathcal{B}({\tau }^{-}\to 3{\pi }^{-}2{\pi }^{+}2{\pi }^0{\nu }_{\tau })<3.4\times {10}^{-6}$ at the 90% confidence level. This is a significant improvement over the previously established limit. In addition, we search for the decay mode ${\tau }^{-}\to 2\omega {\pi }^{-}{\nu }_{\tau }$. We observe 1 event with an expected background of $0.4\genfrac{}{}{0ex}{}{+1.0}{-0.4}$ events and calculate the upper limit $\mathcal{B}({\tau }^{-}\to 2\omega {\pi }^{-}{\nu }_{\tau })<5.4\times {10}^{-7}$ at the 90% confidence level. This is the first upper limit for this mode.

We present measurements of branching fractions and $CP$-violating asymmetries in decays of $B$ mesons to two-body final states containing a $K^0$. The results are based on a data sample of approximately $88\times {10}^6$ ${\rm Y}(4S)\to B\overline{B}$ decays collected with the BABAR detector at the PEP-II asymmetric-energy $B$ Factory at SLAC. We measure $\mathcal{B}(B^{+}\to K^0{\pi }^{+})=(22.3\pm 1.7\pm 1.1)\times {10}^{-6}$, $\mathcal{B}(B^0\to K^0{\pi }^0)=(11.4\pm 1.7\pm 0.8)\times {10}^{-6}$, $\mathcal{B}(B^{+}\to {\overline{K}}^0{K}^{+})<2.5\times {10}^{-6}$, and $\mathcal{B}(B^0\to K^0{\overline{K}}^0)<1.8\times {10}^{-6}$, where the first uncertainty is statistical and the second is systematic, and the upper limits are at the $90\%$ confidence level. In addition, the following $CP$-violating asymmetries have been measured: ${\mathcal{A}}_{CP}(B^{+}\to K^0{\pi }^{+})=-0.05\pm 0.08\pm 0.01$ and ${\mathcal{A}}_{CP}(B^0\to K^0{\pi }^0)=0.03\pm 0.36\pm 0.11$.

We present a study of the decay $B^0\to {\pi }^0{\pi }^0$ based on a sample of $124\times {10}^6$ $B\overline{B}$ pairs recorded by the BABAR detector at the PEP-II asymmetric-energy $B$ Factory at SLAC. We observe $46\pm 13\pm 3$ events, where the first error is statistical and the second is systematic, corresponding to a significance of $4.2$ standard deviations including systematic uncertainties. We measure the branching fraction $\mathcal{B}(B^0\to {\pi }^0{\pi }^0)=(2.1\pm 0.6\pm 0.3)\times {10}^{-6}$, averaged over $B^0$ and ${\overline{B}}^0$ decays.

We present a measurement of $CP$-violating asymmetries in fully reconstructed $B^0\to D^{(*)\pm }{\pi }^{\mp }$ decays in approximately $88\times {10}^6$ ${\rm Y}(4S)\to B\overline{B}$ decays collected with the BABAR detector at the PEP-II asymmetric-energy $B$ factory at SLAC. From a time-dependent maximum-likelihood fit we obtain the following for the $CP$-violating parameters: $a=-0.022\pm 0.038(\mathrm{stat})\pm 0.020(\mathrm{syst})$, $a^{*}=-0.068\pm 0.038(\mathrm{stat})\pm 0.020(\mathrm{syst})$, $c_{\mathrm{lep}}=+0.025\pm 0.068(\mathrm{stat})\pm 0.033(\mathrm{syst})$, and $c_{\mathrm{lep}}^{*}=+0.031\pm 0.070(\mathrm{stat})\pm 0.033(\mathrm{syst})$. Using other measurements and theoretical assumptions we interpret the results in terms of the angles of the Cabibbo-Kobayashi-Maskawa unitarity triangle, and find $|\sin (2\beta +\gamma )|>0.69$ at $68\%$ confidence level. We exclude the hypothesis of no $CP$ violation $[\sin (2\beta +\gamma )=0]$ at $83\%$ confidence level.

We have observed the decays $B\to \phi K$ and $\phi K^{*}$ in a sample of over 45 million $B$ mesons collected with the BABAR detector at the PEP-II collider. The measured branching fractions are $B(B^{+}\to \phi K^{+})=({7.7}_{-1.4\mathrm{}}^{+1.6\mathrm{}}\pm 0.8)\times {10}^{-6\mathrm{}}$, $B(B^0\to \phi K^0)=({8.1}_{-2.5\mathrm{}}^{+3.1\mathrm{}}\pm 0.8)\times {10}^{-6\mathrm{}}$, $B(B^{+}\to \phi K^{*+})=({9.7}_{-3.4\mathrm{}}^{+4.2\mathrm{}}\pm 1.7)\times {10}^{-6\mathrm{}}$, and $B(B^0\to \phi K^{*0\mathrm{}})=({8.7}_{-2.1\mathrm{}}^{+2.5\mathrm{}}\pm 1.1)\times {10}^{-6\mathrm{}}$. We also report the upper limit $B(B^{+}\to \phi {\pi }^{+})<1.4\mathrm{}\times {10}^{-6\mathrm{}}$ ( $90\%$ C.L.).

We present measurements of the branching fractions and charge asymmetries (where appropriate) of two-body B decays to ${\eta }^{(\prime )}{K}^{*},$ ${\eta }^{(\prime )}\rho ,$ ${\eta }^{(\prime )}{\pi }^0,$ $\omega {\pi }^0,$ and $\phi {\pi }^0.$ The data were recorded with the BABAR detector at PEP-II and correspond to $89\times {10}^6$ $B\overline{B}$ pairs produced in $e^{+}{e}^{-}$ annihilation through the ${\rm Y}\mathrm{}\left(4S\right)\mathrm{}$ resonance. We find significant signals for two decay modes and measure the branching fractions $\mathcal{B}{(B}^{+}\to \eta K^{*+})=(25.6\mathrm{}\pm 4.0\pm 2.4)\times {10}^{-6}$ and $\mathcal{B}{(B}^0\to \eta K^{*0})=(18.6\mathrm{}\pm 2.3\pm 1.2)\times {10}^{-6},$ where the first error is statistical and the second systematic. We also find evidence with significance 3.5σ for a third decay mode and measure $\mathcal{B}{(B}^{+}\to \eta {\rho }^{+})=(9.2\mathrm{}\pm 3.4\pm 1.0)\times {10}^{-6}.$ For other channels, we set 90% C.L. upper limits of $\mathcal{B}{(B}^0\to \eta {\rho }^0)<\mathrm{}1.5\mathrm{}\times {10}^{-6},$ $\mathcal{B}{(B}^{+}\to {\eta }^{\prime }{K}^{*+})<\mathrm{}14\mathrm{}\times {10}^{-6},$ $\mathcal{B}{(B}^0\to {\eta }^{\prime }{K}^{*0})<\mathrm{}7.6\mathrm{}\times {10}^{-6},$ $\mathcal{B}{(B}^{+}\to {\eta }^{\prime }{\rho }^{+})<\mathrm{}22\mathrm{}\times {10}^{-6},$ $\mathcal{B}{(B}^0\to {\eta }^{\prime }{\rho }^0)<\mathrm{}4.3\mathrm{}\times {10}^{-6},$ $\mathcal{B}{(B}^0\to \eta {\pi }^0)<\mathrm{}2.5\mathrm{}\times {10}^{-6},$ $\mathcal{B}{(B}^0\to {\eta }^{\prime }{\pi }^0)<\mathrm{}3.7\mathrm{}\times {10}^{-6},$ $\mathcal{B}{(B}^0\to \omega {\pi }^0)<\mathrm{}1.2\mathrm{}\times {10}^{-6},$ and $\mathcal{B}{(B}^0\to \phi {\pi }^0)<\mathrm{}1.0\mathrm{}\times {10}^{-6}.$ For self-flavor-tagging modes with significant signals, the time-integrated charge asymmetries are ${\mathcal{A}}_{\mathrm{ch}}\left(\eta K^{*+}\right)=+0.13\mathrm{}\pm 0.14\pm 0.02$ and ${\mathcal{A}}_{\mathrm{ch}}\left(\eta K^{*0}\right)=+0.02\mathrm{}\pm 0.11\pm \mathrm{0.02.}$

We present a measurement of the time-dependent CP-violating asymmetries in neutral B decays to the ${\pi }^{+}{\pi }^{-}\mathrm{CP}$ eigenstate, and an updated measurement of the charge asymmetry in $B^0\to K^{+}{\pi }^{-}$ decays. In a sample of 33 million ${\rm Y}\mathrm{}\left(4S\right)\mathrm{}\to B\overline{B}$ decays collected with the BABAR detector at the SLAC PEP-II asymmetric B factory, we find ${65}_{-11}^{+12\mathrm{}}$ ${\pi }^{+}{\pi }^{-}$ and $217\pm 18$ $K^{+}{\pi }^{-}$ candidates and measure the asymmetry parameters $S_{\pi \pi }{=0.03\mathrm{}}_{-0.56}^{+0.53\mathrm{}}\pm 0.11,$ $C_{\pi \pi }=-{0.25}_{-0.47}^{+0.45\mathrm{}}\pm 0.14,$ and ${\mathcal{A}}_{K\pi }=-0.07\pm 0.08\pm 0.02,$ where the first error is statistical and the second is systematic.

We present a measurement of the Cabibbo-Kobayashi-Maskawa matrix element $|V_{cb}|$ based on a sample of about 53 700 ${\overline{B}}^0\to D^{*+}{\ell }^{-}{\overline{\nu }}_{\ell }$ decays observed by the BABAR detector. We obtain the branching fraction averaged over $\ell =e,\mu$, $\mathcal{B}({\overline{B}}^0\to D^{*+}{\ell }^{-}{\overline{\nu }}_{\ell })=\mathbf{(}4.90\pm 0.07{(\mathrm{s}\mathrm{t}\mathrm{a}\mathrm{t}.)}_{-0.35}^{+0.36}(\mathrm{s}\mathrm{y}\mathrm{s}\mathrm{t}.)\mathbf{)}\%$. We measure the differential decay rate as a function of $w$, the relativistic boost $\gamma$ of the $D^{*+}$ in the ${\overline{B}}^0$ rest frame. By extrapolating $d\Gamma /dw$ to the kinematic limit $w\to 1$, we extract the product of $|V_{cb}|$ and the axial form factor ${\mathcal{A}}_1(w=1)$. We combine this measurement with a lattice QCD calculation of ${\mathcal{A}}_1(w=1)$ to determine $|V_{cb}|=\mathbf{(}38.7\pm 0.3(\mathrm{s}\mathrm{t}\mathrm{a}\mathrm{t}.)\pm 1.7{(\mathrm{s}\mathrm{y}\mathrm{s}\mathrm{t}.)}_{-1.3}^{+1.5}(\mathrm{\text{theory}})\mathbf{)}\times {10}^{-3}.$

We present measurements of the branching fractions for the Cabbibo suppressed decays $D^{+}\to {\pi }^{+}{\pi }^0$ and $D^{+}\to K^{+}{\pi }^0$ based on a data sample corresponding to an integrated luminosity of $124.3{\mathrm{fb}}^{-1}$. The data were taken with the BABAR detector at the PEP-II $B$ Factory operating on and near the $\mathit{{\rm Y}}(4S)$ resonance. We find $\mathcal{B}(D^{+}\to {\pi }^{+}{\pi }^0)=(1.25\pm 0.10\pm 0.09\pm 0.04)\times {10}^{-3}$ and $\mathcal{B}(D^{+}\to K^{+}{\pi }^0)=(2.52\pm 0.47\pm 0.25\pm 0.08)\times {10}^{-4}$, where the first uncertainty is statistical, the second systematic and the last error is due to the uncertainties in the absolute branching fraction scale for $D^{+}$ mesons. This represents the first observation of the doubly Cabibbo-suppressed $D^{+}\to K^{+}{\pi }^0$ decay mode and a new measurement of the $D^{+}\to {\pi }^{+}{\pi }^0$ branching fraction.

We present an updated measurement of time-dependent $CP$ asymmetries and the $CP$-odd fraction in the decay $B^0\to D^{*+}{D}^{*-}$ using $232\times {10}^{6}B\overline{B}$ pairs collected by the BABAR detector at the SLAC PEP-II $B$ factory. We determine the $CP$-odd fraction to be $0.125\pm 0.044(\mathrm{stat})\pm 0.007(\mathrm{syst})$. The time-dependent $CP$ asymmetry parameters $C_{+}$ and $S_{+}$ are determined to be $0.06\pm 0.17(\mathrm{stat})\pm 0.03(\mathrm{syst})$ and $-0.75\pm 0.25(\mathrm{stat})\pm 0.03(\mathrm{syst})$, respectively. The standard model predicts these parameters to be 0 and $-\sin 2\beta$, respectively, in the absence of penguin amplitude contributions.

We describe searches for $B$ meson decays to the charmless vector-vector final states $\omega K^{*}$, $\omega \rho$, $\omega \omega$, and $\omega \varphi$ with $233\times {10}^6$ $B\overline{B}$ pairs produced in $e^{+}{e}^{-}$ $B\overline{B}$ annihilation at $\sqrt{s}=10.58\mathrm{GeV}$. We also search for the vector-scalar $B$ decay to $\omega f_0$. We measure the following branching fractions in units of ${10}^{-6}$: $\mathcal{B}(B^0\to \omega K^{*0})=2.4\pm 1.1\pm 0.7(<4.2)$, $\mathcal{B}(B^{+}\to \omega K^{*+})={0.6}_{-1.2-0.9}^{+1.4+1.1}(<3.4)$, $\mathcal{B}(B^0\to \omega {\rho }^0)=-0.6\pm {0.7}_{-0.3}^{+0.8}(<1.5)$, $\mathcal{B}(B^{+}\to \omega {\rho }^{+})=10.6\pm {2.1}_{-1.0}^{+1.6}$, $\mathcal{B}(B^0\to \omega \omega )={1.8}_{-0.9}^{+1.3}\pm 0.4(<4.0)$, $\mathcal{B}(B^0\to \omega \varphi )=0.1\pm 0.5\pm 0.1(<1.2)$, and $\mathcal{B}(B^0\to \omega f_0)=0.9\pm {0.4}_{-0.1}^{+0.2}(<1.5)$. In each case the first error quoted is statistical, the second systematic, and the upper limits are defined at the 90% confidence level. For $B^{+}\to \omega {\rho }^{+}$ decays we also measure the longitudinal spin component $f_L=0.82\pm 0.11\pm 0.02$ and the charge asymmetry ${\mathcal{A}}_{CP}=0.04\pm 0.18\pm 0.02$.

The frequency of the 340-${\mathrm{cm}}^{-1\mathrm{}}$ Raman-active O(II)-O(III) ($z$) out-of-phase mode in single-crystal $\mathrm{Y}{\mathrm{Ba}}_2{\mathrm{Cu}}_3{\mathrm{O}}_{7-\delta }$ is measured as a function of magnetic field ($B\leqq 12.7 \mathrm{T}$) and temperature. We reproduce the well-established softening of this mode at $T_c$ and confirm that this anomaly is connected with superconductivity since it reflects the usual $H_{c2\mathrm{}}\mathrm{}\left(T\right)\mathrm{}$ relation. This provides additional evidence for the copper-oxygen planes being the crucial elements for superconductivity in this material. It also suggests strong coupling of this Raman phonon with electronic excitations in the superconductor.

We present measurements of the branching fraction and CP-violating asymmetries for neutral $B$ decays to $D^{*\pm }{D}^{\mp }$. The measurement uses a data sample of approximately $88\times {10}^6$ ${\rm Y}(4S)\to B\overline{B}$ decays collected with the BABAR detector at the SLAC PEP-II asymmetric-energy $e^{+}\mathrm{\text{−}}{e}^{-}$ collider. By fully reconstructing the $D^{*\pm }{D}^{\mp }$ decay products, we measure the branching fraction to be $(8.8\pm 1.0\pm 1.3)\times {10}^{-4}$ and the time-integrated CP-violating asymmetry between the rates to $D^{*-}{D}^{+}$ and $D^{*+}{D}^{-}$ to be $\mathcal{A}=-0.03\pm 0.11\pm 0.05$. We also measure the time-dependent CP-violating asymmetry parameters to be $S_{-+}=-0.24\pm 0.69\pm 0.12$, $C_{-+}=-0.22\pm 0.37\pm 0.10$ for $B\to D^{*-}{D}^{+}$ and $S_{+-}=-0.82\pm 0.75\pm 0.14$, $C_{+-}=-0.47\pm 0.40\pm 0.12$ for $B\to D^{*+}{D}^{-}$. In each case, the first error is statistical and the second error is systematic.

We have measured and calculated the dependence of the Raman phonon intensities of ${\mathrm{YBa}}_2$${\mathrm{Cu}}_3$${\mathrm{O}}_7$ on laser frequency. The local-density approximation and the linear muffin-tin-orbital method were used for the calculations. We find good agreement not only in the absolute phonon intensities in zz or xx/yy polarization but also in the shape of the resonance profiles. These results indicate that the local-density approximation gives an essentially correct description of the band structure and of the electron-phonon interaction ±2 eV around the Fermi energy. We interpret our data in terms of specific interband transitions and estimate the mode mixing.

A Dalitz plot analysis of approximately 12 500 $D^0$ events reconstructed in the hadronic decay $D^0\to {\overline{K}}^0{K}^{+}{K}^{-}$ is presented. This analysis is based on a data sample of $91.5{\mathrm{fb}}^{-1}$ collected with the BABAR detector at the PEP-II asymmetric-energy $e^{+}{e}^{-}$ storage rings at SLAC running at center-of-mass energies on and 40 MeV below the ${\rm Y}(4S)$ resonance. The events are selected from $e^{+}{e}^{-}\to c\overline{c}$ annihilations using the decay $D^{*+}\to D^0{\pi }^{+}$. The following ratio of branching fractions has been obtained: $BR=\frac{\Gamma (D^0\to {\overline{K}}^0{K}^{+}{K}^{-})}{\Gamma (D^0\to {\overline{K}}^0{\pi }^{+}{\pi }^{-})}=(15.8\pm 0.1(\mathrm{stat}.)\pm 0.5(\mathrm{syst}.))\times {10}^{-2}.$ Estimates of fractions and phases for resonant and nonresonant contributions to the Dalitz plot are also presented. The $a_0(980)\to \overline{K}K$ projection has been extracted with little background. A search for $CP$ asymmetries on the Dalitz plot has been performed.

The electronic structures of single-crystal and ceramic samples of the electron-doped superconductor ${\mathrm{Nd}}_{2\mathrm{-}\mathrm{x}}$${\mathrm{Ce}}_{\mathrm{x}}$${\mathrm{CuO}}_{4\mathrm{-}\mathrm{y}}$ with x=0 and 0.15 have been studied using resonant photoemission spectro- scopy. Comparing these spectra with previous results for ${\mathrm{La}}_{2\mathrm{-}\mathrm{x}}$${\mathrm{Sr}}_{\mathrm{x}}$${\mathrm{CuO}}_4$ shows that for both electron and hole doping the Fermi level lies at nearly the same energy, in states that fill in the x=0 insulator gap. We point out that this would occur if the states at the Fermi level obey a Luttinger-type sum rule, i.e., according to standard theory, if the metallic state is a normal Fermi liquid.

We present the analysis of multiple-muon events collected with one supermodule (1013 h live time) and two supermodules (1195 h live time) of the MACRO detector at Gran Sasso, Italy. Multimuon rates are shown to be sensitive to primary-cosmic-ray energies between ∼50 TeV and several thousand TeV. Experimental data are compared with the expected rates from two composition models: a light (i.e., proton-rich) and a heavy (i.e., Fe-rich) composition. The predictions are based on a Monte Carlo simulation of the hadronic interactions of cosmic-ray nuclei, followed by a detailed tracking of the muons through the rock and the experimental apparatus. The results show good sensitivity of the MACRO detector to primary composition. The data exhibit a preference towards the light composition model.