We report the observation of the b -> d penguin-dominated decay B0 -> K*0 K*0bar with a sample of 383.2 +/- 4.2 million BBbar pairs collected with the BaBar detector at the PEP-II asymmetric-energy ...e^+e^- collider at the Stanford Linear Accelerator Center. The measured branching fraction is Br(B0 -> K*0 K*0bar) = 0.49^{+0.16}_{-0.13} +/- 0.05 x 10^{-6} and the fraction of longitudinal polarization f_L (B0 -> K*0 K*0bar) = 0.81^{+0.10}_{-0.12} +/- 0.06. The first error quoted is statistical and the second systematic. We also obtain an upper limit at the 90% confidence level on the branching fraction for Br(B0 ->K*0 K*0) < 0.18 x 10^{-6}.
We report the results of a study of the exclusive charmless semileptonic decay, B --> pi l nu, undertaken with approximately 227 million BBbar pairs collected at the Upsilon(4S) resonance with the ...BaBar detector. The analysis uses events in which the signal B decays are reconstructed with an innovative loose neutrino reconstruction technique. We obtain partial branching fractions in 12 bins of q2, the momentum transfer squared, from which we extract the f+(q2) form-factor shape and the total branching fraction BF(B0 --> pi l nu) = (1.46 +- 0.07(stat) +- 0.08(syst)) x 10^-4. Based on a recent unquenched lattice QCD calculation of the form factor in the range q2 > 16 GeV^2, we find the magnitude of the CKM matrix element |Vub| to be (4.1 +- 0.2(stat) +- 0.2(syst) +0.6-0.4(FF)) x 10^-3, where the last uncertainty is due to the normalization of the form factor.
Muon Collider Forum Report D Li; Maltoni, F; Acosta, D ...
arXiv (Cornell University),
08/2023
Paper, Journal Article
Odprti dostop
A multi-TeV muon collider offers a spectacular opportunity in the direct exploration of the energy frontier. Offering a combination of unprecedented energy collisions in a comparatively clean ...leptonic environment, a high energy muon collider has the unique potential to provide both precision measurements and the highest energy reach in one machine that cannot be paralleled by any currently available technology. The topic generated a lot of excitement in Snowmass meetings and continues to attract a large number of supporters, including many from the early career community. In light of this very strong interest within the US particle physics community, Snowmass Energy, Theory and Accelerator Frontiers created a cross-frontier Muon Collider Forum in November of 2020. The Forum has been meeting on a monthly basis and organized several topical workshops dedicated to physics, accelerator technology, and detector R&D. Findings of the Forum are summarized in this report.
We report a measurement of the time-dependent CP-asymmetry parameters $\cal S$ and $\cal C$ in color-suppressed $B^0 \to D^{(*)0} h^0$ decays, where $h^0$ is a $\pi^0$, $\eta$, or $\omega$ meson, and ...the $D^0$ decays to one of the CP eigenstates $K^+K^-$, $K_S\pi^0$, or $K_S\omega$. The data sample consists of $383\times 10^{6}$ $\Upsilon(4S)\to B\bar{B}$ decays collected with the BABAR detector at the PEP-II asymmetric-energy $B$-factory at SLAC. The results are ${\cal S}= -0.56 \pm 0.23 \pm 0.05$ and ${\cal C}= -0.23\pm 0.16\pm 0.04$, where the first error is statistical and the second is systematic.
We study the time-dependent Dalitz plot of D->KSpi+pi- in B0->D(*)h0 decays, where h0 is a pi0, eta, eta', or omega meson and D*->Dpi0 using a data sample of 383 X 10^6 Upsilon(4S)->BBbar decays ...collected with the BABAR detector. We determine cos2beta = 0.42+-0.49+-0.09+-0.13, sin2beta = 0.29+-0.34+-0.03+-0.05, and |lambda| = 1.01+-0.08+-0.02, where the first error is statistical, the second is the experimental systematic uncertainty, and the third, where given, is the Dalitz model uncertainty. Assuming the world average value for sin2beta and |lambda|=1, cos2beta>0 is preferred over cos2beta<0 at 86% confidence level.
A search for the neutrinoless, lepton-flavor violating decay of the tau lepton into three charged leptons has been performed using 376 fb^{-1} of data collected at an e^+e^- center-of-mass energy ...around 10.58 GeV with the BaBar detector at the PEP-II storage rings. In all six decay modes considered, the numbers of events found in data are compatible with the background expectations. Upper limits on the branching fractions are set in the range (4-8) x 10^{-8} at 90% confidence level.
We report the results of a CP violation analysis of the decay B+/- --> D(pipipi0)K+/-, where D(pipipi0) indicates a neutral D meson detected in the final state pi+pi-pi0, excluding K_S pi0. The ...analysis makes use of 324 million e+e- --> BB events recorded by the BaBar experiment at the PEP-II e+e- storage ring. By analyzing the pi+pi-pi0 Dalitz plot distribution and the B+/- --> D(pipipi0)K+/- branching fraction and decay rate asymmetry, we calculate parameters related to the phase gamma of the CKM unitarity triangle. We also measure the magnitudes and phases of the components of the D0 --> pi+pi-pi0 decay amplitude.
We analyze the decay B0 --> K+ K- K0 using 383 million B-Bbar events collected by the BaBar detector at SLAC to extract CP violation parameter values over the Dalitz plot. Combining all K+ K- K0 ...events, we find A_CP = -0.015 +/- 0.077 +/- 0.053 and beta_eff = 0.352 +/- 0.076 +/- 0.026 rad, corresponding to a CP violation significance of 4.8 sigma. A second solution near pi/2 - beta_eff is disfavored with a significance of 4.5 sigma. We also report A_CP and beta_eff separately for decays to phi(1020) K0, f0(980) K0, and K+ K- K0 with m_{K+ K-} > 1.1 GeV/c^2.
We present a search for the lepton flavor violating decay B+ --> K+ tau-/+ mu+/- using 383 million B Bbar events collected by the BABAR experiment. The branching fraction for this decay can be ...substantially enhanced in new physics models. The kinematics of the tau from the signal B decay are inferred from the K+, mu, and other B in the event, which is fully reconstructed in one of a variety of hadronic decay modes, allowing the signal B candidate to be fully reconstructed. We observe no excess of events over the expected background and set a limit of B(B+ --> K+ tau mu) < 7.7 x 10^-5 at 90% confidence level, where the branching fraction is for the sum of the K+ tau- mu+ and K+ tau+ mu- final states.
We present measurements of the branching fractions for the decays B+/- --> a1(1260)+/- pi0 and B+/- --> a1(1260)0 pi+/- from a data sample of 232 * 10^6 BB pairs produced in e+e- annihilation through ...the Y(4S) resonance. We measure the branching fraction B(B+/- --> a1(1260)+/- pi0) * B(a1(1260)+/- --> pi- pi+ pi+/-) = (13.2 +/- 2.7 +/- 2.1) * 10^-6 with a significance of 4.2 sigma, and the branching fraction B(B+/- --> a1(1260)0 pi+/-) * B(a1(1260)0 --> pi- pi+ pi0) = (20.4 +/- 4.7 +/- 3.4) * 10^-6 with a significance of 3.8 sigma, where the first error quoted is statistical and the second is systematic.
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