Measurement of the e+e- --> hadrons cross-section at low energy with ISR events at BABAR
Bogdan Malaescu
备注：
On behalf of the BABAR Collaboration. Proceeding of the 11th International Workshop on Tau Lepton Physics - Manchester, UK, 13-17 September 2010. 6 pages, 3 figures
The precise measurement of the cross section e+e- --> pi+ pi-(gamma) from threshold to an energy of 3 GeV, using events with Initial State Radiation (ISR) collected with the BABAR detector, is presented. The ISR luminosity is determined from a study of the leptonic process e+e- --> mu+ mu- gamma(gamma), and the method is tested by the comparison with the next-to-leading order (NLO) QED prediction. The leading-order hadronic contribution to the muon magnetic anomaly calculated using the BABAR pi pi cross section measured from threshold to 1.8 GeV is (514.1 +- 2.2(stat) +- 3.1(syst)) * 10^{-10}. Other results on ISR multihadronic cross sections from BABAR are presented.
The status of the ISR analysis with BaBar is presented. Preliminary results are given on the process e+e- --> 2pi+ 2pi- and J/psi decays including a determination of its total width and the branching ratios into 2pi+ 2pi-, K+ K- pi+ pi-, and 2K+ 2K- modes.
The ISR method has been largely exploited by the BABAR experiment, for measuring numerous channels of the cross section e+e- into hadrons. For the pi+pi-(gamma) and K+K-(gamma) channels, BABAR has pioneered the method based on the ratio between the hadronic mass spectra and the mu+mu-(gamma) one. This method allows to cancel many systematic uncertainties in the ratio, hence the precise measured cross sections. Many multihadronic channels have also been studied using the ISR method, and cross sections have been published. These experimental results have also been exploited for phenomenological …
We present preliminary measurements of the cross sections for e+e- --> KS KL pi0 and KS KL pi0 pi0 obtained using the technique of Initial State Radiation with 469 fb^-1 of e+e- collision data collected with the BABAR detector at or near the Upsilon(4S) resonance. The resonant substructure of KS KL pi0 is investigated, and branching fractions for the decays of the charmonium resonances J/psi and psi(2S) into these final states are measured.
We present a review of BaBar results on e+e- annihilations into exclusive hadronic final states using the initial state radiation technique. Cross sections over the sqrt{s} range from threshold to 4.5 GeV, with very small point-to-point systematic errors, are presented for the 3pi, 2(pi+ pi-), 3(pi+ pi-), 2(pi+ pi-)2pi0, K+ K- pi+ pi-, 2(K+ K-) and p anti-p final states. The proton form factor and the ratio of its electric and magnetic components are also presented.
A method of measuring e+e- annihilation cross sections at low energy sqrt{s}< 5 GeV, using initial-state radiation, is described. Experimental data from the PEP-II B-factory at 10.6 GeV center-of-mass energy, obtained via ISR, are presented. The cross sections are measured for many processes e+e- --> 3pi, 4pi, 2K pi, 2K 2pi, 4K, p anti-p, Lambda anti-Lambda, D anti-D, ... . From the measured cross sections the parameters of known resonances are improved, the baryons form factors are derived and compared with theory predictions. New states, e.g; Y(4260) and Y(2175), for which the internal struc…
A preliminary analysis of low-energy $\ep\en$ collision data produced via initial state radiation (ISR) has been performed using 22 $fb^{-1}$ of \babar data. The selection of data samples corresponding to the $\mumu$, $\pipi$, $\kk$, $p \bar p$, $\kkπ^0$, 3$π$, 4$π$, 5$π$, 6$π$, 7$π$ final states accompanied by the emitted ISR hard photon has been demonstrated. The invariant mass of the hadronic final state defines the effective collision c.m. energy, and so \babar ISR data can be compared to the relevant direct $\ep\en$ measurements. The resulting distributions are already competitive with DC…
Two new hadronic cross sections measured by the BaBar experiment are presented: $e^+e^- \to π^+π^-π^0π^0$ and $e^+e^- \to π^+π^-η$. For both channels, the contribution the anomalous magnetic moment of the muon is calculated.
A precise measurement of the cross section for the process e+e- --> K+K-(gamma) from threshold to an energy of 5 GeV is obtained with the initial-state radiation (ISR) method using 232 fb^{-1} of data collected with the BaBar detector at e+e- center-of-mass energies near 10.6 GeV. The measurement uses the effective ISR luminosity determined from the e+e- --> mu+mu-(gamma)gamma_ISR process with the same data set. The corresponding lowest-order contribution to the hadronic vacuum polarization term in the muon magnetic anomaly is found to be a_mu^{KK, LO}=(22.93 +- 0.18_{stat} +- 0.22_{syst}) * 1…
A precise measurement of the cross section of the process $e^+e^-\toπ^+π^-(γ)$ from threshold to an energy of 3GeV is obtained with the initial-state radiation (ISR) method using 232fb$^{-1}$ of data collected with the BaBar detector at $e^+e^-$ center-of-mass energies near 10.6GeV. The ISR luminosity is determined from a study of the leptonic process $e^+e^-\toμ^+μ^-(γ)γ_{\rm ISR}$, which is found to agree with the next-to-leading-order QED prediction to within 1.1%. The cross section for the process $e^+e^-\toπ^+π^-(γ)$ is obtained with a systematic uncertainty of 0.5% in the dominant $ρ$ re…
A precise measurement of the cross section of the process e+ e- to pi+ pi- (gamma) from threshold to an energy of 3 GeV is obtained with the initial state radiation (ISR) method using 232 fb^-1 of data collected with the BABAR detector at e+ e- center-of-mass energies near 10.6 GeV. The ISR luminosity is determined from a study of the leptonic process e+ e- to mu+ mu- gamma (gamma). The leading-order hadronic contribution to the muon magnetic anomaly calculated using the pi pi cross section measured from threshold to 1.8 GeV is (514.1 +-2.2(stat} +-3.1(syst}) x 10^{-10}.
Initial state radiation (ISR) plays an important role in $e^+$$e^-$ collision experiments such as the BESIII. To correct the ISR effects in measurements of hadronic cross-sections of $e^+e^-$ annihilation, an iterative method that weights simulated ISR events is proposed here to assess the efficiency of event selection and the ISR correction factor for the observed cross-section. The simulated ISR events were generated only once, and the obtained cross-sectional line shape was used iteratively to weigh the same simulated ISR events to evaluate the efficiency and corrections until the results c…
We present measurements of branching fraction, polarization and charge asymmetry in charmless hadronic B decays with eta, eta', omega, and b_1 in the final state. All the results use the final BABAR dataset.
We report recent measurements of branching fractions and charge asymmetries of charmless hadronic B decays using the data collected with the BABAR detector at the PEP-II asymmetric energy e+e- collider.
We review hadron spectroscopy at BABAR with emphasis on recent results from the studies of the X(3872) state, inclusive charmonia on recoil, double charmonium production, and the broad structure observed at around 4.26 GeV/c^2. These results are preliminary, unless otherwise specified.
Recent measurements of branching fractions and CP-violating partial-rate asymmetries for rare hadronic B-meson decays by the asymmetric-energy B-factory experiments, Belle and BaBar, are reviewed.
We present preliminary measurements of the branching fractions for charmless hadronic decays of B mesons into two-body final states with kaons, pions and a phi resonance. The measurements are based on a data sample of approximately 23 million B-anti-B pairs collected by the BABAR detector at the PEP-II asymmetric B Factory at SLAC.
Recent results on the search for pentaquarks and on charmonium spectroscopy at BaBar are reviewed. The latter includes the observation of the puzzling new state X(3872) -> J/psi pi+ pi- in B decays, and the searches for X(3872) in two-body B decays and initial state radiation events.
We present experimental measurements of branching fraction and longitudinal polarization fraction in charmless hadronic B decays into vector, axial vector and tensor final states with the final dataset of \babar . Measurements of such kind of decays are a powerful tool both to test the Standard Model and search possible sources of new physics.
We present recent results on charmless hadronic B decays using data collected by the BaBar detector at the PEP-II asymmetric-energy e+e- collider at the Stanford Linear Accelerator Center. We report measurements of branching fractions and charge asymmetries in several charmless two-body, three-body, and quasi-two-body decay modes. We also report measurements of polarization in charmless B decays to exclusive final states with two vector mesons.
We report on recent results in spectroscopy from BaBar. This includes the discovery of a new $Λ_c$ baryon, detailed studies of the $D^*_{sJ}(2317)^+$, $D_{sJ}(2460)^+$, X(3872) and Y(4260) particles and the first measurement of hadronic non-$B\bar{B}$ decays of the $Υ(4S)$ meson.
We review recent results of the BABAR and BELLE Collaborations on the the alpha and gamma angles of the unitary triangle, on the B to K pi pi Dalitz-plot analyses, and on the searches for baryonic B decays and for B to DD decays.
We report measurements of Time-Dependent CP asymmetries in several $b\to s$ penguin dominated hadronic B decays, where New Physics contributions may appear. We find no significant discrepancies with respect to the Standard Model expectations.
In this paper the studies of three different B decays to hadronic states are presented. These results are based on 1999-2003 dataset collected by the BaBar experiment at the PEP-II e+e- storage ring at the Stanford Linear Accelerator Center. The measurements are the hadronic branching fraction of B+ -> J/psi p Lambda-bar, B0 -> J/psi p p-bar, B0 -> D*+D-, and the direct CP-asymmetry in B0 -> D0(CP) K- channels.
The BaBar experiment at SLAC is designed to measure CP violation in the B meson system, however the very high statistics combined with the different electron and positron beam energies, the detector design and the open trigger allow a wide variety of spectroscopic measurements. We are beginning to tap this potential via several production mechanisms. Here we present recent results from initial state radiation, hadronic jets, few body B and D hadron decays, and interactions in the detector material. We also summarize measurements relevant to Ds meson spectroscopy, pentaquarks and charmonium spe…
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.
A program of measuring the light hadrons production in exclusive $e^+e^-$ to hadrons processes is in place at BaBar with the aim to improve the calculation of the hadronic contribution to the muon $g-2$. We present the most recent results obtained by using the full data set of about $514 \mathrm{fb}^{-1}$ collected by the BaBar experiment at the PEP-II $e^+e^-$ collider at a center-of-mass energy of about $10.6$ GeV. In particular, we report the results on the channels $e^+e^-\rightarrow π^+ π^- 3π^0$, $e^+e^-\rightarrow π^+π^- 2π^0η$, and its resonant sub-states. These final states are studie…
We report on measurements of branching fractions for several hadronic tau decays to final states with kaons, which can be used to determine the strange quark mass and the element |V_us| of the Cabibbo-Kobayashi-Maskawa quark-mixing matrix. The results are obtained from data collected with the BaBar and Belle detectors at the PEP-II and KEKB asymmetric-energy e+e- colliders at SLAC and KEK, respectively, both operating at center-of-mass energies near the Y(4S) resonance.
We present preliminary measurements of time-dependent CP-violation parameters in the decays B0->omegaK0S, B0->eta'K0, B0->pi0K0S, B0->phiK0Spi0, and B0->K+K-K0S, which includes the resonant final states phiK0S and f0(980)K0S. The data sample corresponds to the full BABAAR dataset of 467 million BBbar pairs produced at the PEP-II asymmetric-energy e+e- collider at the Stanford Linear Accelerator Center.
We review recent experimental results on Bd and Bs mesons decays by the BaBar and Belle experiments. These include measurements of the color-suppressed decays B0bar to D(*)0h0, h0=pi0, eta, etaprime, omega, observation of the baryonic decay B0bar to Lambdac+ Lambdabar K-, measurements of the charmless decays B to eta h, h=K, pi, B to Kpi and observation of CP eigenstates in the Bs decays: B0s to J/psi f0(980), B0s to J/psi f0(1370) and B0s to J/psi eta. The theoretical implications of these results will be considered.
We present results from BABAR experiment for the measurement of inclusive and exclusive branching fractions of B mesons into final states containing $J/ψ$, $ψ(2S)$ and $χ_c$. The contributions of CP even and odd amplitudes in the decay $B^0 \to J/ψK^{*0}$ are determined from an angular analysis. We report the measurements of the branching ratios $B^0 \to D^{*+}D^{*-}$ and $D^{*+}D^{*-}K^0_S$, and the study of exclusive two-body and quasi-two-body charmless decays. The branching fraction of the decay $B^0 \to K^{*0} γ$ has been determined and the corresponding CP asymmetry has been measured.
Using 13.3 fb^-1 of e+e- collision data taken in the Upsilon(1S-4S) region with the CLEO III detector at the CESR collider, a search has been made for the new resonance Y(4260) recently reported by the BaBar Collaboration. The production of Y(4260) in initial state radiation (ISR), and its decay into pi+pi-J/psi are confirmed. A good quality fit to our data is obtained with a single resonance. We determine M(Y(4260))=(4284+17-16(stat)+-4(syst)) MeV/c^2, Gamma(Y(4260))=(73+39-25(stat)+-5(syst)) MeV/c^2, and Gamma_ee(Y(4260))xBr(Y(4260)->pi+pi-J/psi)=(8.9+3.9-3.1(stat)+-1.9(syst)) eV/c^2.
We present a summary of the hadronic cross section measurements performed with BaBar at the PEP-II collider via radiative return. BaBar has performed measurements of exclusive final states containing 3, 4 and 6 hadrons via this complementary method, as well as a measurement of the proton form factor.
Using 22.7M BBbar events collected with the BABAR detector at SLAC, we present preliminary measurements of the branching fractions for charmless hadronic decays of B mesons into two-body, quasi two-body and three-body final states with pions, kaons, and rho and a0 resonances. In the search for exclusive $B^0 \to π^+π^-π^0$, we measure ${\cal B}(B^0 \to ρ^{\pm}(770)π^{\mp})=(28.9\pm5.4\pm4.3) \times 10^{-6}$, together with the relative asymmetry ${\cal A}_{\rm phys} = -0.04 \pm 0.18 \pm 0.02$. We also set the upper limits on $B^0 \to ρ^0(770)π^0$, non-resonant $B^0 \to π^+π^-π^0$, $B^0 \to a_0^…
The measurement of exclusive $e^+e^-$ to hadrons processes is a significant part of the physics program of $BABAR$ experiment, aimed to improve the calculation of the hadronic contribution to the muon $g-2$ and to study the intermediate dynamics of the processes. We present the most recent results obtained by using the full data set of about 470\,fb$^{-1}$ collected by the BABAR detector at the PEP-II $e^+e^-$ collider at a center-of-mass energy of about 10.6 GeV. In particular, we report the results on $e^+e^-$ annihilation into six- and seven-pion final states. The study of the very rich dyn…
New Babar results on exclusive e+e- -> hadrons reactions at low c.m. energy with a baryon-antibaryon or K\bar{K} pair in the final state are presented. Cross sections are measured using the initial state radiation technique from the threshold up to 4--5 GeV. From the measured e+e- -> proton\antiproton, Lambda\Lbar, Sigma0\Sigbar0, Lambda\Sigbar0(Sigma0\Lbar) cross sections we derive effective baryon form factors and compare them with predictions. We measure the K\bar{K}π(η), K+K-ππ, K+K-3π, K+K-4π, K+K-K+K- final states and also study their internal structure. A new Y(2175) state is observed i…
The {\it BaBar} experiment has recorded the decays of more than 465$\times 10^6 B\bar{B}$ pairs since 1999, and is reaching an unprecedented precision in the measurement of hadronic B decays. The following results are presented: tests of QCD factorization with the decays $B\to χ_{c0}K^{*} $, $B\to χ_{c1,2}K^{(*)} $, and $\bar{B}^{0}\to D^{(*)0}h^{0}$, $h^0=π^0, η,\ ω, η'$, study of the decays to charmonium $B\to η_c K^{(*)},\ η_c(2S) K^{(*)}$ and $h_cK^{(*)}$, measurement of the mass difference between neutral and charged $B$'s, measurement of the "r" parameters for the extraction of the CKM a…
The status of analysis of processes with hard photon emitted from the initial state (ISR) at BABAR is presented. We tag events by the presence of a hard photon in the detector, then reconstruct mu+mu- and several exclusive hadronic final states. The invariant mass of the final state determines an effective collision center of mass energy at which these measurements can be compared with results from direct e+e- annihilation process. The first results on e+e- --> 2h+2h-, where h=pi,K and on e+e- --> J/psi, obtained with a sample of 89.3/fb, are presented. Measurements of inclusive eta, pi+, K+ a…
The BABAR collaboration has nearly completed a program of precise measurements of the cross sections for the dominant channels of e+e- --> hadrons from threshold to an energy of 3-5 GeV using the initial-state radiation (ISR) method, i.e. the measurement of the cross sections e+e- --> gamma hadrons with the energetic photon detected at large angle to the beams. These data are used as input to vacuum polarization dispersion integrals, in particular the hadronic contribution to the muon g-2 anomaly. In addition to the recently measured pi+pi- cross section, giving the dominant contibution, many …
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.
Recent BaBar measurements on lifetime and mixing of B mesons are reported. Various techniques are used, ranging from the full reconstruction of hadronic B decays, to partial reconstruction techniques, and to a totally inclusive approach with dilepton events. The results presented are based on a data sample collected by BaBar during the 1999-2000 data taking, and should be considered as preliminary.
Inclusive hadron production cross sections in e+e-collisions shed light on the fundamental fragmentation and hadronization processes. We present measurements of the inclusive spectra of charged pions, kaons and protons in hadronic events at a center-of-mass energy of 10.54 \gev. These results are compared with theoretical predictions and the predictions of three hadronization models. Along with previous measurements at higher energies, they are also used to study the scaling properties of hadron production.
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.
A precise measurement of the ratio of hadron to muon production in e^+e^- collisions, denoted by R(s), is a necessary input for the interpretation of current precision electroweak measurements. We describe a method for measuring R(s) with the BaBar detector at the PEP-II B-factory using initial-state radiation events.
We report updates on two analyses of inclusive semileptonic B decays based on a dataset of 89 million BB events recorded with the BABAR detector at the Y(4S) resonance. Events are selected by fully reconstructing the decay of one B meson and identifying a charged lepton from the decay of the other B meson. In the first analysis, the measurement of the first and second moment of the hadronic mass distribution in Cabibbo-favored B ->X_c l nu decays allows for the determination of the nonperturbative parameters $\barΛ$ and $λ_1$ of Heavy Quark Effective Theory (HQET) and |Vcb|. In the second anal…
Charge asymmetry in processes e+ e- --> mu+ mu- gamma and e+ e- --> pi+ pi- gamma is measured using 232 fb-1 of data collected with the BABAR detector at center-of-mass energies near 10.58 GeV. An observable is introduced and shown to be very robust against detector asymmetries while keeping a large sensitivity to the physical charge asymmetry that results from the interference between initial and final state radiation. The asymmetry is determined as afunction of the invariant mass of the final-state tracks from production threshold to a few GeV/c2. It is compared to the expectation from QED f…
The BaBar Collaboration has an intensive program of studying hadronic cross sections at low-energy $e^+e^-$ collisions, accessible via initial-state radiation. Our measurements allow significant improvements in the precision of the predicted value of the muon anomalous magnetic moment, that shed light on the current $\approx$ 3.5 sigma difference between the predicted and the experimental values. We have published results on a number of processes with two to six hadrons in the final state. We report here the results of recent studies with the final states that constitute the main contribution …
The BaBar Collaboration has an intensive program studying the cross sections of hadron production in low-energy e+e- annihilation, accessible via initial-state radiation. Our measurements allow a significant improvement in the precision of the predicted value of the muon anomalous magnetic moment. These improvements are necessary for shedding light on the current > 3 sigma difference between the predicted and the experimental values. We have published results on a number of processes with two to six hadrons in the final state, and other final states are currently under investigation. We report…
We present preliminary BaBar measurements of hadronic cross sections in $e^+e^-$ annihilation using the radiative return technique. The cross sections for $e^+e^- \to p\bar{p} $, $ 3(π^+π^-)$, $ 2(π^+π^-)2π^0$, and $ K^+K^-2(π^+π^-)$ are measured. Measurements of the proton form factor and of the ratio $G_E/G_M$ are also shown.
Numerous channels of the cross section e+e- --> hadrons have been measured by the BABAR experiment using the ISR method. For the pi+pi-(gamma) and K+K-(gamma) channels, BABAR has pioneered the method based on the ratio between the hadronic mass spectra and mu+mu-(gamma). Many systematic uncertainties cancel in the ratio, hence the precise measured cross sections. These measurements have been exploited for phenomenological studies, like the determination of the hadronic contribution to the anomalous magnetic moment of the muon (g-2)_mu.
The BaBar collaboration has an extensive program of studying hadronic cross sections in low-energy e+e- collisions, accessible via initial-state radiation. Our measurements allow significant improvements in the precision of the predicted value of the muon anomalous magnetic moment. These improvements are necessary for illuminating the current ~3.6 sigma difference between the predicted and the experimental values. We have published results on a number of processes with two to six hadrons in the final state. We report here the results of recent studies with final states that constitute the main…
The $B^0\bar{B^0}$ oscillation frequency $Δm_d$ has been measured with the BaBar detector at the PEP-II asymmetric $B$ factory with different experimental techniques. The discussion here is focused on the recent simultaneous measurement of $Δm_d$ and $τ_{B^0}$ with exclusively reconstructed $B^0 \to D^{*-}l^+ν_l$ decays, based on 23 million $B\bar{B}$ pairs collected by BaBar. The measurements of $Δm_d$ with fully reconstructed hadronic decays and with dilepton events are also reviewed. The average BaBar result is $Δm_d = 0.500 \pm 0.008 \pm 0.006$ $ps^{-1}$.
BABAR, the detector for the SLAC PEP-II asymmetric e+e- B Factory operating at the upsilon 4S resonance, was designed to allow comprehensive studies of CP-violation in B-meson decays. Charged particle tracks are measured in a multi-layer silicon vertex tracker surrounded by a cylindrical wire drift chamber. Electromagentic showers from electrons and photons are detected in an array of CsI crystals located just inside the solenoidal coil of a superconducting magnet. Muons and neutral hadrons are identified by arrays of resistive plate chambers inserted into gaps in the steel flux return of the …
We present several recent results from the BaBar collaboration in the areas of initial state radiation physics and transition form factors. An updated study of the processes e+e- -> K+K-pi+pi- and e+e- -> K+K-pi0pi0 provides an improved understanding of the Y(2175) meson. A very precise study of the process e+e- -> pi+pi- improves the precision on the calculated anomalous magnetic moment of the muon and provides by far the best information on excited rho states. Our previous measurements of the timelike transition form factors (TFF) of the eta and eta' mesons at Q^2=112 GeV^2, combined with ne…
Selected results from tau analyses performed using the BaBar detector at the SLAC National Accelerator Laboratory are presented. A precise measurement of the tau mass and the tau{+} tau{-} mass difference is undertaken using the hadronic decay mode tau- --> pi+ pi- pi- nu. In addition an investigation into the strange decay modes tau- --> K0S pi- pi0 nu and tau- --> K0S pi- nu is also presented, including a fit to the tau- --> K0S pi-nu invariant mass spectrum. Precise values for the Mass and Width of the K*(892) are obtained.
We present preliminary measurements of CP-violating asymmetries in B decays. These include new results on the CKM angle alpha based on studies of the decay B -> rho+ rho- and several charmonium and hadronic penguin modes, sensitive to the CKM angle beta, including results on B -> phi K0S, B -> K+K-K0, B -> eta' K0S, B -> f0 K0, and B -> pi0 K0S. We also report on several of results related to the extraction of gamma and (2*beta+gamma) and present limits on CPT violation in B decays.
