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NEXT Collaboration(Henriques, C. A. O. et al), Benlloch-Rodriguez, J. M., Carcel, S., Carrion, J. V., Diaz, J., Felkai, R., et al. (2022). Neutral Bremsstrahlung Emission in Xenon Unveiled. Phys. Rev. X, 12(2), 021005–23pp.
Abstract: We present evidence of non-excimer-based secondary scintillation in gaseous xenon, obtained using both the NEXT-White time projection chamber (TPC) and a dedicated setup. Detailed comparison with first-principle calculations allows us to assign this scintillation mechanism to neutral bremsstrahlung (NBrS), a process that is postulated to exist in xenon that has been largely overlooked. For photon emission below 1000 nm, the NBrS yield increases from about 10(-2) photon/e(-) cm(-1) bar(-1) at pressure-reduced electric field values of 50 V cm(-1) bar(-1) to above 3 x 10(-1) photon/e(-) cm(-1) bar(-1) at 500 V cm(-1) bar(-1). Above 1.5 kV cm(-1) bar(-1), values that are typically employed for electroluminescence, it is estimated that NBrS is present with an intensity around 1 photon/e(-) cm(-1) bar(-1), which is about 2 orders of magnitude lower than conventional, excimer-based electroluminescence. Despite being fainter than its excimeric counterpart, our calculations reveal that NBrS causes luminous backgrounds that can interfere, in either gas or liquid phase, with the ability to distinguish and/or to precisely measure low primary-scintillation signals (S1). In particular, we show this to be the case in the "buffer region, where keeping the electric field below the electroluminescence threshold does not suffice to extinguish secondary scintillation. The electric field leakage in this region should be mitigated to avoid intolerable levels of NBrS emission. Furthermore, we show that this new source of light emission opens up a viable path toward obtaining S2 signals for discrimination purposes in future single-phase liquid TPCs for neutrino and dark matter physics, with estimated yields up to 20-50 photons/e(-) cm(-1).
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BABAR Collaboration(del Amo Sanchez, P. et al), Azzolini, V., Lopez-March, N., Martinez-Vidal, F., Milanes, D. A., & Oyanguren, A. (2010). B-meson decays to eta ' rho, eta ' f(0), and eta ' K*. Phys. Rev. D, 82(1), 011502–8pp.
Abstract: We present measurements of B-meson decays to the final states eta'rho, eta'f(0), and eta'K*, where K* stands for a vector, scalar, or tensor strange meson. We observe a significant signal or evidence for eta'rho(+) and all the eta'K* channels. We also measure, where applicable, the charge asymmetries, finding results consistent with no direct CP violation in all cases. The measurements are performed on a data sample consisting of 467 X 10(6) B (B) over bar pairs, collected with the BABAR detector at the PEP-II e(+)e(-) collider at the SLAC National Accelerator Laboratory. Our results favor the theoretical predictions from perturbative QCD and QCD factorization and we observe an enhancement of the tensor K-2*(1430) with respect to the vector K*(892) component.
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BABAR Collaboration(del Amo Sanchez, P. et al), Lopez-March, N., Martinez-Vidal, F., & Oyanguren, A. (2011). Measurement of partial branching fractions of inclusive charmless B meson decays to K+, K-0, and pi(+). Phys. Rev. D, 83(3), 031103–8pp.
Abstract: We present measurements of partial branching fractions of B -> K+ X, B -> (KX)-X-0, and B -> pi(+) 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-physics particles which could enter the b -> s(d) loop transitions. The analysis is performed on a data sample consisting of 383 X 10(6)B (B) over bar pairs collected with the BABAR detector at the PEP-II e(+)e(-) asymmetric energy collider. We observe the inclusive B -> pi(+) X process, and we set upper limits for B -> K+ X and B -> (KX)-X-0. Our results for these inclusive branching fractions are consistent with those of known exclusive modes, and exclude large enhancements due to sources of new physics.
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BABAR Collaboration(del Amo Sanchez, P. et al), Lopez-March, N., Martinez-Vidal, F., & Oyanguren, A. (2011). Measurements of branching fractions, polarizations, and direct CP-violation asymmetries in B+ -> rho K-0*(+) and B+ -> f(0)(980)K*(+) decays. Phys. Rev. D, 83(5), 051101–8pp.
Abstract: We present measurements of the branching fractions, longitudinal polarization, and direct CP-violation asymmetries for the decays B+ -> rho K-0*(+) and B+ -> f(0)(980)K*(+) with a sample of (467 +/- 5) x 10(6)B (B) over bar pairs collected with the BABAR detector at the PEP-II asymmetric-energy e(+)e(-) collider at the SLAC National Accelerator Laboratory. We observe B+ -> rho K-0*(+) with a significance of 5: 3 sigma and measure the branching fraction B(B+ -> rho K-0*(+)) = (4.6 +/- 1.0 +/- 0.4) x 10(-6), the longitudinal polarization f(L) = 0.78 +/- 0.12 +/- 0.03, and the CP-violation asymmetry A(CP) = 0.31 +/- 0.13 +/- 0.03. We observe B+ -> f(0)(980)K*(+) and measure the branching fraction B(B+ -> f(0)(980)K*(+)) x B(f(0)(980) -> pi(+)pi(-)) = (4.2 +/- 0.6 +/- 0.3) x 10(-6) and the CP-violation asymmetry A(CP) = 0.15 +/- 0.12 +/- 0.03. The first uncertainty quoted is statistical and the second is systematic.
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BABAR Collaboration(del Amo Sanchez, P. et al), Lopez-March, N., Martinez-Vidal, F., Milanes, D. A., & Oyanguren, A. (2012). Observation and study of the baryonic B-meson decays B -> D(*) p(p)over-bar (pi)(pi). Phys. Rev. D, 85(9), 092017–21pp.
Abstract: We present results for B-meson decay modes involving a charm meson, protons, and pions using 455 x 10(6) B (B) over bar pairs recorded by the BaBar detector at the SLAC PEP-II asymmetric-energy e(+)e(-) collider. The branching fractions are measured for the following ten decays: (B) over bar (0) -> D-0 p (p) over bar, (B) over bar (0) -> D*(0) p (p) over bar, (B) over bar (0) -> D+ p (p) over bar pi(-) , (B) over bar (0) -> D-0 p (p) over bar pi(-) , B- -> D-0 p (p) over bar pi(-) , B- -> D*(0) p (p) over bar pi(-) , (B) over bar (0) -> D-0 p (p) over bar pi(-) pi(+) , (B) over bar (0) -> D*(0) p (p) over bar pi(-) pi(+) B- -> D+ p (p) over bar pi(-) pi(-) , and B- -> D*(0) p (p) over bar pi(-) pi(-). The four B- and the two five-body (B) over bar (0) modes are observed for the first time. The four-body modes are enhanced compared to the three- and the five-body modes. In the three-body modes, the M(p (p) over bar) and M(D-(*)0 p) invariant- mass distributions show enhancements near threshold values. In the four-body mode (B) over bar (0) -> D+ p (p) over bar pi(-) , the M(p pi(-)) distribution shows a narrow structure of unknown origin near 1: 5 GeV/c(2). The distributions for the five-body modes, in contrast to the others, are similar to the expectations from uniform phase-space predictions.
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