Search for Dark Matter in Upsilon Decays at BABAR Experiment
Romulus Godang
备注：
Contributed to the Proceedings of the 16th International Conference on Topics in Astroparticle and Underground Physics, Toyama, Japan. This work was supported by the U.S. Department of Energy
Recent investigations have suggested that the singlet six-quark combination $uuddss$ may be a deeply bound state $S$, called Sexaquark. An essentially stable state $S$ is a potentially excellent Dark Matter candidate. We present the first search for a stable, doubly strange six-quark state in the decays of $Υ(4S) \to Λ\barΛ$. Based on a data sample of $Υ(2S)$ and $Υ(3S)$ decays collected by the BABAR Experiment we report the most recent results and set stringent limits on the existence of such exotic particle.
BaBar experiment scan around the Upsilon(4S) resonance and measure its mass and full width. They also measure Br(Upsilon(4S) -> B0 B0b) = 0.486 +/- 0.010 +/- 0.009 from 81.7 fb-1 Upsilon(4S) data. CLEO collaboration took about 0.42 fb-1 Upsilon(5S) data. They search for B_s in both inclusive and exclusive modes and find evidence for B_s production at the Υ(5S) and Br(Upsilon(5S) -> B_s^(*) B_s^(*)b) = (21 +/- 3 +/- 9)%.
In this paper we present two searches for new physics in Upsilon(3S) decays collected by the BABAR detector. We search for charged lepton-flavour violating decays of the Upsilon(3S), which are unobservable in the Standard Model but are predicted to occur in several beyond-the-Standard Model scenarios. We also search for production of a light Higgs or Higgs-like state produced in radiative decays of the Upsilon(3S) and decaying to muon pairs.
Using a sample of 122 million Upsilon(3S) decays collected with the BaBar detector at the PEP-II asymmetric energy collider at the SLAC National Accelerator Laboratory, we measure the ratio R_taumu=BR(Upsilon(1S)->tau^+tau^-)/BR(Upsilon(1S)->mu^+mu^-); the measurement is intended as a test of lepton universality and as a possible search for a light pseudoscalar Higgs boson in Next to Minimal Supersymmetric Standard Model (NMSSM) scenarios. Such a boson could appear in a deviation of the ratio R_taumu from the Standard Model expectation, that is 1, except for small lepton mass corrections. The …
Based on a data sample of 81.7 fb^-1 collected at the Upsilon(4S) resonance with the BABAR detector at the PEP-II asymmetric-energy B Factory at SLAC, we present the current status of the measurement of the branching fraction of Upsilon(4S) to B0bar B^0. Our study of the decay was performed through the exclusive decays B0bar to D^{*+} \ell^{-} barν_{\ell} using a partial reconstruction method, where the D^{*+} is detected only through the soft pion daughter from the decay D^{*+} to D^{0} pi^{+}.
We describe a measurement of the time-integrated luminosity of the data collected by the BABAR experiment at the PEP-II asymmetric-energy e+e- collider at the Upsilon(4S), Upsilon(3S) and Upsilon(2S) resonances and in a continuum region below each resonance. We measure the time-integrated luminosity by counting e+e- --> e+e- and (for the Upsilon(4S) only) e+e- --> mu+mu- candidate events, allowing additional photons in the final state. We use data-corrected simulation to determine the cross sections and reconstruction efficiencies for these processes, as well as the major backgrounds. Due to t…
Recent investigations have suggested that the six-quark combination uuddss could be a deeply bound state (S) that has eluded detection so far, and a potential dark matter candidate. We report the first search for a stable, doubly strange six-quark state in Upsilon -> S anti-Lambda anti-Lambda decays based on a sample of 90 million Upsilon(2S) and 110 million Upsilon(3S) decays collected by the BABAR experiment. No signal is observed, and 90% confidence level limits on the combined Upsilon(2S,3S) -> S anti-Lambda anti-Lambda branching fraction in the range (1.2-1.4)x10^-7 are derived for m_S < …
After nine years of operation the BABAR experiment at the B factory PEPII (Standford Linear Accelerator Center) stopped data taking in April 2008. The last three month of data taking were devoted to e+e- collisions at center of mass energies of the Upsilon(2S), Upsilon(3S) and to an energy scan above the Upsilon(4S). Besides the observation of the bottomonium ground state eta_b, the center of mass energy dependent e+e- -> b bbar cross section was measured in the energy range from 10.54 to 11.20 GeV. BELLE observed an enhancement in the production cross section for e+e- -> Upsilon(nS) pi+ pi- -…
The ratio $R_{τμ}(Υ(1S)) = Γ_{Υ(1S)\toτ^+τ^-}/Γ_{Υ(1S)\toμ^+μ^-}$ is measured using a sample of $(121.8\pm1.2)\times10^6$ $Υ(3S)$ events recorded by the BABAR detector. This measurement is intended as a test of lepton universality and as a search for a possible light pseudoscalar Higgs boson. In the standard model (SM) this ratio is expected to be close to 1. Any significant deviations would violate lepton universality and could be introduced by the coupling to a light pseudoscalar Higgs boson. The analysis studies the decays $Υ(3S)\toΥ(1S)π^+π^-$, $Υ(1S)\to l^+l^-$, where $l=μ,τ$. The result,…
We present the first observation of the bottomonium ground state eta_b(1S) in the photon energy spectrum using a sample of 109+/-1 million of Upsilon(3S) events recorded at the Upsilon(3S) energy with the BaBar detector at the PEP-II B factory at SLAC. A peak at E_gamma = 921.2 {+2.1}{-2.8}(stat) +/- 2.4(syst) MeV observed with a significance of 10 standard deviations in the photon energy spectrum is interpretated as being due to the radiative transition Upsilon(3S) -> gamma eta_b(1S). This photon energy corresponds to an eta_b(1S) mass of 9388.9 {+3.1}{-2.3}(stat) +/- 2.7(syst) MeV/c2. The hy…
Time-dependent B0-antiB0 flavor oscillations and B0 and B+ lifetimes are studied in a sample of fully reconstructed B mesons collected with the BaBar detector, running at the PEP-II asymmetric e+e- B Factory with center-of-mass energies near the Upsilon(4S) resonance. This is the first time that time-dependent mixing and lifetime measurements have been performed at Upsilon(4S) energies.
We search for evidence of a light Higgs boson (A0) in the radiative decays of the narrow Upsilon(3S) resonance: Upsilon(3S) -> gamma A0, where A0 -> invisible or A0 -> mu+mu-. Such an object appears in extensions of the Standard Model, where a light CP-odd Higgs boson naturally couples strongly to b-quarks. We find no evidence for such processes in a sample of 122 million Upsilon(3S) decays collected by the BaBar collaboration at the PEP II B-factory, and set 90% C.L. upper limits on the product of the corresponding branching fractions. We also set a limit on the di-muon branching fraction of …
Spectroscopy results for Belle and BaBar are reported. A particular focus is put on new results of the X(3872) state with its radiative decays to $J$/$ψ$$γ$ and $ψ'$$γ$, its decay into $J$/$ψ$3$π$ and the search for production in radiative Upsilon decays. Another focus is $L$=2 mesons, in particlar a possible $D$-wave assignment to the X(3872) and the confirmation of an Upsilon $D$-wave state.
We present recent results on exclusive Bbar -> Xc l- nubar_l decays and measurements of the CKM matrix element |Vcb| based on data collected at the Upsilon(4S) resonance with the babar detector at the PEP-II e+e- storage rings.
We present recent results of hadronic B meson decays related to the CKM angle beta. The data used were collected by the BABAR detector at the pepII asymmetric-energy e+e- collider operating at the Upsilon(4S) resonance located at the Stanford Linear Accelerator Center.
We report the first measurement of the branching fraction f00 for Upsilon(4S) --> B0B0bar. The data sample consists of 81.7 fb^-1 collected at the Upsilon(4S) resonance with the BABAR detector at the PEP-II asymmetric-energy e^+e^- storage ring. Using partial reconstruction of the decay B0bar --> D^{*+} \ell^{-} \barν_{\ell} in which only the charged lepton and the soft pion from the decay D^{*+} --> D0 pi^+ are reconstructed, we obtain f00 = 0.487 \pm 0.010(stat) \pm 0.008(sys). Our result does not depend on the branching fractions of B0bar --> D^{*+} \ell^{-} \barν_{\ell} and D^{*+} --> D0 p…
We search for invisible decays of the Upsilon(1S) meson using a sample of 91.4 x 10^{6} Upsilon(3S) mesons collected at the BaBar/PEP-II B-factory. We select events containing the decay Upsilon(3S) -> pi+ pi- Upsilon(1S) and search for evidence of an undetectable Upsilon(1S) decay recoiling against the dipion system. We set an upper limit on the branching fraction BR(Upsilon(1S) -> invisible) < 3.0 x 10^{-4} at the 90% confidence level.
We present evidence, from published BABAR data, for the existence of further excitations in the b-bbar spectrum, namely the long-awaited Upsilon(1D) and Upsilon(2D) with central masses of 10098 pm 5 MeV and 10492 pm 5 MeV, respectively. The significance of the Upsilon(1 3D1) and Upsilon(2 3D1) signals is found to be 3.0 and 10.7 standard deviations, respectively.
Bound upsilon states and their decays provide a unique laboratory for testing QCD, LQCD, and quarkonium potential models. I review recent results, some of which are significant improvements in precision over previous measurements and others are first-time observations. While most of the results presented are from CLEO III there are also notable contributions from BaBar and Belle who have just begun to exploit their strong capabilities for studying bound state upsilons.
We present branching fraction and CP asymmetry results for a variety of B decays based on up to 56.4 fb^-1 collected by the BaBar experiment running near the Upsilon(4S) resonance at the PEP-II e+e- B-factory.
We report about the studies of the decay channels B- -> D0 K-, B0 -> D*- a1+ and B0 -> Ds(*)- pi+ with a sample of 62.10^6 Upsilon(4S) decays into B meson pairs collected with the BaBar detector at the PEP II asymmetric e+ e- collider.
New BABAR results on B mesons and quarkonia are presented: an analysis of B+ --> X(3872)K+ and B0 --> X(3872)K0 decays with X(3872) --> J/Psi pi+pi-, a precise measurement of the B mass difference Delta mB = m(B0) - m(B+) and a study of hadronic transition between Upsilon mesons.
I present three recent results from searches for exotic physics at the BaBar/PEP-II B-factory. These results span many of the samples produced at the B-factory, including B mesons, tau leptons, and Upsilon(3S) mesons. We have searched for CPT-violation in B mixing and find no significant deviation from the no-violation hypothesis. We have also searched for lepton-flavor-violating decays of the tau using tau- -> omega l- and tau- -> l+ l- l+ and their charge conjugates. We find no evidence for these processes and set upper limits on their branching fractions. Finally, we have searched for a low…
We present recent measurements of the CKM angle alpha using data collected by the BABAR detector at the PEP-II asymmetric-energy e^+e^- collider at the SLAC National Accelerator Laboratory, operating at the Upsilon(4S) resonance. We present constraints on alpha from B->pipi, B->rhorho and B->rhopi decays.
We present branching fraction and CP asymmetry results for a variety of charmless B decays based on up to 124 fb^-1 collected by the BABAR experiment running near the Upsilon(4S) resonance at the PEP-II e+e- B-factory.
Charged lepton-flavor violating processes are extremely rare in the Standard Model, but they may occur in several beyond-the-Standard Model theories, including Supersymmetry or models with leptoquarks or compositeness. We present a search for such processes in a sample of 117M Upsilon(3S) decays recorded with the BaBar detector. We place upper limits on the branching fractions BF(Upsilon(3S) -> e tau) < 5.0e-6 and BF(Upilon(3S) -> mu tau) < 4.1e-6 at 90% confidence level. These results are used to place lower limits on the mass scale of beyond-the-Standard Model physics contributing to lepton-…
Recent results obtained using the data sample collected on the Upsilon(4S) resonance with the Belle detector at the KEKB asymmetric-energy e^+ e^- collider and the Babar detector at the PEP-II asymmetric-energy e^+ e^- collider are discussed. Measurements of several charmless and charmed baryonic B decay branching fractions are reported, and some behaviors and mechanisms are discussed.
Several new-physics (NP) models predict the existence of low-mass Higgs states and light dark matter candidates. Previous BABAR searches have given null results for these new states and have excluded large regions of the NP models parameter space. We report on new searches on light Higgs and light dark matter at BABAR using the 516 1/fb of data collected with the BABAR detector at the PEP-II asymmetric-energy e+e- collider at the SLAC National Accelerator Laboratory.
The BABAR detector, situated at the SLAC PEP-II asymmetric e^+e^- collider, has been recording data at energies on and around the Upsilon(4S) resonance since May 1999. In this paper, we briefly describe the PEP-II B Factory and the BABAR detector. The performance presently achieved by the experiment in the areas of tracking, vertexing, calorimetry and particle identification is reviewed. Analysis concepts that are used in the various papers submitted to this conference are also discussed.
We present a preliminary measurement of the resonance parameters of the Upsilon(10580) resonance with the BABAR detector at the SLAC PEP-II asymmetric B factory. We measure the total decay width to be (20.7 +- 1.6 +- 2.5) MeV, the partial electronic width to be (0.321 +- 0.017 +- 0.029) kev and the mass to be (10.5793 +- 0.0004 +- 0.0012) GeV.
A brief review of experimental results on charmonium and charmonium-like hadron spectroscopy at B-factories is presented. A special focus is put on recent results of eta_c and eta_c(2S) study, X(3872) radiative decays, omega J/psi final state study and search for charmonium production in radiative Upsilon decays.
We report a measurement of the production ratio of charged and neutral B mesons from Upsilon(4S) decays based on the ratio of efficiency-corrected yields for the charmonium modes J/psi K^+ and J/psi K^{0}_{S} with 81.9 fb^-1 of data collected with the BABAR detector on the Upsilon(4S) resonance at 10.580 GeV. We find a value of 1.006 +/- 0.036 (stat) +/- 0.031 (sys) for the ratio R^{+/0}=Gamma(Upsilon(4S) -> B^+ B^-)/Gamma(Upsilon(4S)->B^0 B^0bar).
Using CLEO data, we report on the confirmation of the eta_b(1S0) ground state of bottomonium in the radiative decay Upsilon(3S) -> gamma eta_b. We determine its mass to be M(eta_b) = 9391.8 +- 6.6 +- 2.1 MeV, which corresponds to the hyperfine splitting Delta M_hf(1S) = 68.5 +- 6.6 +- 2.0 MeV, and the branching fraction B(Upsilon(3S) -> gamma eta_b) = (7.1 +- 1.8 +- 1.1) x 10^-4. These results agree with those previously reported by BaBar.
We present a preliminary measurement of time-dependent CP-violating asymmetries in B^0-->J/psi K_S and B^0-->psi(2S) K_S decays recorded by the BABAR detector at the PEP-II asymmetric B Factory at SLAC. The data sample consists of 9.0 fb-1 collected at the Upsilon(4S) resonance and 0.8 fb-1 off-resonance. One of the neutral B mesons, produced in pairs at the Upsilon(4S), is fully reconstructed. The flavor of the other neutral B meson is tagged at the time of its decay, mainly with the charge of identified leptons and kaons. The time difference between the decays is determined by measuring the …
We report measurements of charmonium resonances (J/Psi, Psi(2S),Chi_c1) using about 25 fb^-1 of data collected by the BABAR detector around the Upsilon(4S) resonance. We present measurements of inclusive charmonium production of charmonium in B decays and from the continuum, as well as exclusive branching ratios of B mesons into charmonium final states. We present also a measurement of the B0 -> K*0 gamma branching ratio and a search for the decay B0 -> gamma gamma.
We search for single-photon decays of the Upsilon(1S) resonance, Upsilon->gamma+invisible, where the invisible state is either a particle of definite mass, such as a light Higgs boson A0, or a pair of dark matter particles, chi chi-bar. Both A0 and chi are assumed to have zero spin. We tag Upsilon(1S) decays with a dipion transition Upsilon(2S)->pi+pi-Upsilon(1S) and look for events with a single energetic photon and significant missing energy. We find no evidence for such processes in the mass range m_A0<=9.2 GeV and m_chi<=4.5 GeV in the sample of 98e6 Upsilon(2S) decays collected with the B…
We study inclusive di-pion decays using a sample of 108 x 10^6 Upsilon(3S) events recorded with the BABAR detector. We search for the decay mode Upsilon(3S) --> pi+ pi- h_b(1P) and find no evidence for the bottomonium spin-singlet state h_b(1P) in the invariant mass distribution recoiling against the pi+ pi- system. Assuming the h_b(1P) mass to be 9.900 GeV/c^2, we measure the upper limit on the branching fraction B[Upsilon(3S) --> pi+ pi- h_b(1P)] < 1.2 x 10^{-4}, at 90% confidence level. We also investigate the chi_{bJ}(2P) --> pi+ pi- chi_{bJ}(1P), Upsilon(3S) --> pi+ pi- Upsilon(2S), and U…
We search for evidence of a light scalar boson in the radiative decays of the Upsilon(2S) and Upsilon(3S) resonances: Upsilon(2S,3S)-> gamma A0, A0 -> mu^+ mu^-. Such a particle appears in extensions of the Standard Model, where a light CP-odd Higgs boson naturally couples strongly to b-quarks. We find no evidence for such processes in the mass range 0.212<= m(A0)<= 9.3 GeV in the samples of 99*10^6 Upsilon(2S) and 122*10^6 Upsilon(3S) decays collected by the BABAR detector at the PEP-II B-factory and set stringent upper limits on the effective coupling of the b quark to the A0. We also limit …
We present preliminary results on hadronic decays of B mesons, based on data recorded at the Upsilon(4S) resonance with the BABAR detector at the PEP-II B-factory at SLAC. We measure branching fractions of many B decay modes, including decays to J/psi phi K, J/psi pi^+ pi^- and eta_c K final states. We report the observation of the decay B --> D_s pi^- and the first measurement of the flavor-tagged D meson production in B^0 decays. Since their preliminary nature, the results presented in this paper are based on different data samples.
We search for a low-mass scalar CP-odd Higgs boson, A0, produced in the radiative decay of the Upsilon resonance and decaying into a tau+tau- pair: Upsilon(1S)->gamma A0. The production of Upsilon(1S) mesons is tagged by Upsilon(2S)->pi+pi-Upsilon(1S) transitions, using a sample of (98.3+/-0.9) million Upsilon(2S) mesons collected by the BaBar detector. We find no evidence for a Higgs boson in the mass range 3.5 GeV<= m(A0)<=9.2 GeV, and combine these results with our previous search for the tau decays of the light Higgs in radiative Upsilon(3S) decays, setting limits on the coupling of A0 to …
We present several searches for charmless hadronic two-body and three-body decays of B mesons from electron-positron annihilation data collected by the BABAR detector near the Upsilon(4S) resonance. We report the preliminary branching fractions BR(B0 --> pi+pi-) = (4.1 +/- 1.0 +/- 0.7) x 10^-6, BR(B0 --> K+pi-) = (16.7 +/- 1.6 +/- 1.3) x 10^-6, BR(B0 --> rho-/+ pi+/-) = (49 +/- 13 +6 -5) x 10^-6, BR(B+ --> eta' K+) = (62 +/- 18 +/- 8) x 10^-6, and present upper limits for nine other decays.
We report a preliminary branching fraction of (1.80 +/- 0.37(stat.) +/- 0.23(syst.)) x 10^-4 for the charmless exclusive semileptonic B+ -> pi0 l+ nu decay, where l can be either a muon or an electron. This result is based on data corresponding to an integrated luminosity of 81 fb^-1 collected at the Upsilon(4S) resonance with the BABAR detector. The analysis uses BBbar events that are tagged by a B meson reconstructed in the semileptonic B- -> D0 l- nubar (X) decays, where X can be either a gamma or a pi0 from a D* decay.
We present the results of a search for the decay B0 --> tau+tau- in a data sample of (232 +- 3) x 10^6 Upsilon(4S) --> BBbar decays using the BABAR detector. Certain extensions of the Standard Model predict measurable levels of this otherwise rare decay. We reconstruct fully one neutral B meson and seek evidence for the signal decay in the rest of the event. We find no evidence for signal events and obtain B(B0 --> tau+tau-) < 4.1 x 10^-3 at the 90% confidence level.
We have performed a search for the eta_b(1S) meson in the radiative decay of the Upsilon(2S) resonance using a sample of 91.6 million Upsilon(2S) events recorded with the BABAR detector at the PEP-II B factory at the SLAC National Accelerator Laboratory. We observe a peak in the photon energy spectrum at E_gamma = 609.3 {+4.6} {-4.5} (stat) +/- 1.9 (syst) MeV, corresponding to an eta_b(1S) mass of 9394.2 {+4.8} {-4.9} (stat) +/- 2.0 (syst) MeV/c^2. The branching fraction for the decay Upsilon(2S) --> gamma eta_b(1S) is determined to be [3.9 +/-1.1 (stat) {+1.1} {-0.9} (syst)] x 10^(-4). We fin…
Many models of physics beyond the Standard Model predict the existence of new Abelian forces with new gauge bosons mediating interactions between "dark sectors" and the Standard Model. We report a search for a dark boson Z' coupling only to the second and third generations of leptons in the reaction e+e- -> mu+mu- Z', Z' -> mu+mu- using 514 fb-1 of data collected by the BABAR experiment. No significant signal is observed for Z' masses in the range 0.212 - 10 GeV. Limits on the coupling parameter g' as low as 7x10^-4 are derived, leading to improvements in the bounds compared to those previousl…
Based on a data sample of an integrated luminosity of 57.4 fb-1 at the Upsilon(4S) resonance taken with the BaBar detector using the SLAC PEP-II asymmetric-energy $B$-Factory, hadronic decays of B meson with the final states D(*) and three pions are studied. The study is performed by fully reconstructing the exclusive decays of B->D(*)a_{1}(1260) and the non-resonant modes B->D(*)rho^{0} pi and B->D(*)pipipi. The current status of the study is presented and a dominant B->D(*)a_{1}(1260) decay is shown.
Several types of new-physics models predict the existence of light dark matter candidates and low-mass Higgs states. Previous \babar searches for invisible light-Higgs decays have excluded large regions of model parameter space. We present searches for a dark-sector Higgs produced in association with a dark gauge boson and searches for a light Higgs in $Υ(nS)$ decays.
We calculate the inclusive decay width of $Υ\to l^+ l^-$. Then we get the ratio $R_{τμ}=Γ[Υ\to τ^+τ^-]/ Γ[Υ\to μ^+μ^-]$ to ${\cal{O}}(α)$ and ${\cal{O}}(α_s^2)$ within the Standard Model(SM). Comparing with the recent Babar's data $R_{τμ}=1.005\pm0.013\pm 0.022$, we find that SM prediction $R_{τμ}$ is not consistent with the experimental data in the error bar. The discrepancy is about $1.25σ$. So leptonic decay of $Υ$ may be a possible signature of New Physics(NP). We present a better approach to test the Standard Model, $R_{τμ}(E_{soft})=.Γ[Υ\to τ^+τ^-+X]/ Γ[Υ\to μ^+μ^-+X]|_{E_X<E_{soft}}$. A…
Invisible psi and Upsilon decays into light neutralinos, within the MSSM or N(n)MSSM, are smaller than for nu nubar production, even if light spin-0 particles are coupled to quarks and neutralinos. In a more general way, light dark matter particles are normally forbidden, unless they can annihilate sufficiently through a new interaction stronger than weak interactions (at lower energies), as induced by a light spin-1 U boson, or heavy-fermion exchanges in the case of scalar dark matter. We discuss the possible contributions of U-boson, heavy-fermion, or spin-0 exchanges to invisible psi and Up…
We study the rare B meson decays B{+-,0} --> J/ψ K^+ K^- K{+-,0}, B{+-,0} --> J/ψ ϕ K{+-,0}, and search for B0 --> J/ψ ϕ, using 469 million BBbar events collected at the Upsilon(4S) resonance with the BABAR detector at the PEP-II e+e- asymmetric-energy collider. We present new measurements of branching fractions and a study of the J/ψϕmass distribution in search of new charmonium-like states. In addition, we search for the decay B0 --> J/ψ ϕ, and find no evidence of a signal.
We report a measurement of the branching fraction e^+e^- --> B0B0bar with a data sample of 81.7 fb^-1 collected at the Upsilon(4S) resonance with the BABAR detector at the PEP-II asymmetric-energy e^+e^- storage ring. Using partial reconstruction of the decay B0bar --> D^{*+} \ell^{-} \barν_{\ell} we obtain a preliminary result of f00 = 0.486 +- 0.010(stat.) +- 0.009(sys.). Our result does not depend on branching fractions of the B0bar and the D^{*+} decay chains, on the simulated reconstruction efficiency, on the ratio of the charged and neutral B meson lifetimes, nor on assumption of isospin…
We search for a light scalar particle produced in single-photon decays of the Upsilon(3S) resonance through the process Upsilon(3S) -> gamma A0, A0 -> invisible. Such an object appears in Next-to-Minimal Supersymmetric extensions of the Standard Model, where a light CP-odd Higgs boson naturally couples strongly to b-quarks. If, in addition, there exists a light, stable neutralino, decays of A0 could be preferentially to an invisible final state. We search for events with a single high-energy photon and a large missing mass, consistent with a 2-body decay of Upsilon(3S). We find no evidence for…
We present measurements of the inclusive semileptonic branching fractions of charged and neutral B mesons using 20.6 fb-1 of data measured at the Upsilon(4S) with the BABAR detector. Events are tagged with a fully reconstructed hadronic decay of a B meson. The correlation between the flavor of the tag B meson and the electron charge allows the separation of prompt semileptonic B decays and cascade semileptonic charm decays. We obtain the preliminary inclusive semileptonic branching fraction of charged B mesons b+ = 0.103+/-0.006+/-0.005, neutral B mesons b0 = 0.104+/-0.008+/-0.005, their avera…
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 99M Y(2S) decays and 117M Y(3S) decays collected with the BABAR detector. We place upper limits on the branching fractions BF(Y(nS) -> e tau) and BF(Y(nS) -> mu tau) (n = 2, 3) at the 10^(-6) level and use these results to place lower limits of order 1 TeV on the mass scale of charged lepton flavor violating e…
We report the results of a search for the bottomonium ground state eta_b(1S) in the photon energy spectrum with a sample of (109 +/- 1) million of Upsilon(3S) recorded at the Upsilon(3S) energy with the BABAR detector at the PEP-II B factory at SLAC. We observe a peak in the photon energy spectrum at E_gamma = 921.2 {+2.1} {-2.8} (stat) +/- 2.4(syst) MeV with a significance of 10 standard deviations. We interpret the observed peak as being due to monochromatic photons from the radiative transition Upsilon(3S) -> gamma eta_b(1S). This photon energy corresponds to an eta_b(1S) mass of $9388.9 {+…
We perform a measurement of the tau -> l gamma nu anti-nu (l = e, mu) branching fractions for a minimum photon energy of 10 MeV in the tau rest frame, using 431fb^-1 of e^+e^- collisions collected at the center-of-mass energy of the Upsilon(4S) resonance with the BaBar detector at the PEP-II storage rings. We find B(tau -> mu gamma nu anti-nu ) = (3.69pm0.03pm0.10)x10^-3, and B(tau -> e gamma nu anti-nu ) = (1.847pm0.015pm0.052)x10^-2, where the first quoted error is statistical, and the second is systematic. These results are substantially more precise than previous measurements.
A recent update from MiniBooNE has strengthened the observed $4.8σ$ excess of $e$-like events. Motivated by this and other notable deviations from standard model predictions, such as the muon $(g-2)$, we propose a solution to low energy anomalies through a dark neutrino sector. The model is renormalizable and can also explain light neutrino masses with an anomaly-free and dark $U(1)^\prime$ gauge symmetry broken at the GeV scale. Large kinetic mixing leads to s-channel production of heavy neutral leptons at $e^+e^-$ colliders, where we point out and explain a $\gtrsim 2σ$ excess observed in th…
The BaBar collaboration has analysed 60M BB_ pairs collected at the Upsilon (4S) resonance at the PEP II asymetric collider at SLAC. Using this data sample we have measured the CP violation parameters sin (2beta)=0.75+/- 0.09 (STAT) +/-0.04 (SYST) and lambda =0.92+/- 0.06 (STAT) +/- 0.02 (SYST) from B0 to cc_+K*0 + c.c. decays. From charmless 2-body B decays we measure A_Kpi =-0.05 +/- 0.06 +/- 0.01(-0.14,+0.05), S_pipi = -0.01 +/- 0.37 +/- 0.07(-0.66,+0.62), C_pipi =-0.02 +/- 0.29 +/- 0.07(-0.54,+0.48). A number of B lifetime and mixing parameters, extracted from subsamples of this data set, …
We summarize recent results by the BABAR and Belle Collaborations on the search for CP violation and new physics beyond the Standard Model in several rare B meson decays. The measurements exploit the final BABAR and Belle Upsilon(4S) datasets, which consist of approximately 470 and 772 million BBbar pairs, respectively.
We report on preliminary measurements of time-dependent CP asymmetries in neutral B decays to CP eigenstates with transition amplitudes that are dominated by penguin-type loops. The results are obtained from a data sample of up to 227 million Upsilon(4S)->BB-bar decays collected with the BABAR detector at the PEP-II asymmetric-energy B-meson Factory at SLAC. The amplitudes of the effective mixing-induced CP asymmetries, sin(2beta)_eff, are derived from decay-time distributions of events in which one neutral B meson is fully reconstructed in a final state without charm and the other B meson is …
We perform a measurement of the branching fractions for tau -> l gamma nu anti-nu (l= e, mu) decays for a minimum photon energy of 10 MeV in the tau rest frame using 430 fb^-1 of e^+ e^- collisions collected at the center-of-mass energy of the Upsilon(4S) resonance around 10.58GeV with the BaBar detector at the PEP-II storage rings. We find B(tau -> mu gamma nu nu) = (3.69pm0.03pm0.10)x10^-3 and B(tau -> e gamma nu anti-nu) = (1.847pm0.015pm0.052)x10^-2 where the first quoted error is statistical and the second is systematic. These results represent a substantial improvement with respect to ex…
