Measurement of branching fractions of hadronic decays of the Ω c 0 baryon
Not Available
72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
Engineering topics
Li, Y.
Publications and source records attributed to Li, Y..
The Pandora multi-algorithm approach to automated pattern recognition of cosmic-ray muon and neutrino events in the MicroBooNE detector
The development and operation of Liquid-Argon Time-Projection Chambers for neutrino physics has created a need for new approaches to pattern recognition in order to fully exploit the imaging capabilities offered by this technology. Whereas the human brain can excel at identifying features in the recorded events, it is a significant challenge to develop an automated, algorithmic solution. The Pandora Software Development Kit provides functionality to aid the design and implementation of pattern-recognition algorithms. It promotes the use of a multi-algorithm approach to pattern recognition, in which individual algorithms each address a specific task in a particular topology. Many tens of algorithms then carefully build up a picture of the event and, together, provide a robust automated pattern-recognition solution. This paper describes details of the chain of over one hundred Pandora algorithms and tools used to reconstruct cosmic-ray muon and neutrino events in the MicroBooNE detector. Metrics that assess the current pattern-recognition performance are presented for simulated MicroBooNE events, using a selection of final-state event topologies.
72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
Measurement of the τ lepton polarization and R ( D * ) in the decay B ¯ → D * τ − ν ¯ τ with one-prong hadronic τ decays at Belle
Not Available
72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
Design and performance of the spin asymmetries of the nucleon experiment
The Spin Asymmetries of the Nucleon Experiment (SANE) performed inclusive, double-polarized electron scattering measurements of the proton at the Continuous Electron Beam Facility at Jefferson Lab. A novel detector array observed scattered electrons of four-momentum transfer 2.5 < Q 2 < 6.5 GeV 2 and Bjorken scaling 0.3 < x < 0.8 from initial beam energies of 4.7 and 5.9 GeV. Employing a polarized proton target which could be rotated with respect to the incident electron beam, both parallel and near perpendicular spin asymmetries were measured, allowing model-independent access to transverse polarization observables A 1 , A 2 , g 1 , g 2 and moment d 2 of the proton. This article summarizes the operation and performance of the polarized target, polarized electron beam, and novel detector systems used during the course of the experiment, and describes analysis techniques utilized to access the physics observables of interest.
43 PARTICLE ACCELERATORS↗
Search for light tetraquark states in Y ( 1 S ) and Y ( 2 S ) decays
We search for the J PC = 0 – – and 1 +– light tetraquark states with masses up to 2.46 GeV/c 2 in Υ(1S) and Υ(2S) decays with data samples of (102 ± 2) million and (158 ± 4) million events, respectively, collected with the Belle detector. No significant signals are observed in any of the studied production modes, and 90% credibility level (C.L.) upper limits on their branching fractions in Υ(1S) and Υ(2S) decays are obtained. The inclusive branching fractions of the Υ(1S) and Υ(2S) decays into final states with f 1 (1285) are measured to be B(Υ(1S) → f 1 (1285) + anything) = (46 ± 28(stat) ± 13(syst)) × 10 –4 and B(Υ(2S) → f 1 (1285) + anything) = (22 ± 15(stat) ± 6.3(syst)) × 10 –4 . The measured χ b2 → J/ψ + anything branching fraction is measured to be (1.50 ± 0.34(stat) ± 0.22(syst)) × 10 –3 , and 90% C.L. upper limits for the χ b0,b1 → J/ψ + anything branching fractions are found to be 2.3 × 10 –3 and 1.1 × 10 –3 , respectively. For B(χ b1 → ω + anything), the branching fraction is measured to be (4.9 ± 1.3(stat) ± 0.6(syst)) × 10 –2 . All results reported here are the first measurements for these modes.
72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
Measurement of cosmic-ray reconstruction efficiencies in the MicroBooNE LArTPC using a small external cosmic-ray counter
The MicroBooNE detector is a liquid argon time projection chamber at Fermilab designed to study short-baseline neutrino oscillations and neutrino-argon interaction cross-section. Due to its location near the surface, a good understanding of cosmic muons as a source of backgrounds is of fundamental importance for the experiment. We present a method of using an external 0.5 m (L) x 0.5 m (W) muon counter stack, installed above the main detector, to determine the cosmic-ray reconstruction efficiency in MicroBooNE. Data are acquired with this external muon counter stack placed in three different positions, corresponding to cosmic rays intersecting different parts of the detector. The data reconstruction efficiency of tracks in the detector is found to be $\epsilon_{\mathrm{data}}=(97.1\pm0.1~(\mathrm{stat}) \pm 1.4~(\mathrm{sys}))\%$, in good agreement with the Monte Carlo reconstruction efficiency $\epsilon_{\mathrm{MC}} = (97.4\pm0.1)\%$. This analysis represents a small-scale demonstration of the method that can be used with future data coming from a recently installed cosmic-ray tagger system, which will be able to tag $\approx80\%$ of the cosmic rays passing through the MicroBooNE detector.
47 OTHER INSTRUMENTATION↗
Giant reversible magnetocaloric effect in the pyrochlore Er 2 Mn 2 O 7 due to a cooperative two-sublattice ferromagnetic order
Most magnetic refrigeration materials showing a large and reversible magnetocaloric effect (MCE) undergo a second-order ferromagnetic (FM) transition involving large-moment magnetic species on one sublattice. Furthermore, a stronger MCE is expected near a cooperative FM order of two or more magnetic species with large magnetic moments residing on different sublattices, but experimental realizations are rare. Here we report on the discovery of large MCE in the cubic pyrochlore Er 2 Mn 2 O 7 near its second-order FM transition at T c ≈ 34K; under the magnetic field change of 1 and 5 T, the maximum magnetic entropy change –ΔS M is 5.27 and 16.1Jkg –1 K –1 , and the estimated magnetic refrigerant capacity reaches 68 and 522Jkg –1 , respectively. These latter values are among the largest for the known MCE materials. The observed giant and reversible MCE in Er 2 Mn 2 O 7 is mainly attributed to the large saturation moment of 18.9μ B per formula unit owing to a simultaneous FM ordering of the rear-earth Er 3+ and transition-metal Mn 4+ localized moments. Our results suggest that Er 2 Mn 2 O 7 pyrochlore is a promising candidate for magnetic refrigeration applications in the temperature range 20–80 K. More importantly, this work provides a new material system for developing high-performance MCE materials that can exhibit a strongly coupled FM transition involving two magnetic sublattices of large local moments in a single-phase material.
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
Measurement of the decays B → η ℓ ν ℓ and B → η ' ℓ ν ℓ in fully reconstructed events at Belle
We report branching fraction measurements of the decays B + → ηℓ + νℓ and B + → η'ℓ + νℓ based on 711 fb –1 of data collected near the Υ(4S) resonance with the Belle experiment at the KEKB asymmetric-energy e + e – collider. This data sample contains 772 million BB¯ events. One of the two B mesons is fully reconstructed in a hadronic decay mode. Among the remaining (“signal-B”) daughters, we search for the η meson in two decay channels, η → γγ and η → π + π – π 0 , and reconstruct the η' meson in η' → ηπ + π – with subsequent decay of the η into γγ. Combining the two η modes and using an extended maximum likelihood, the B + → ηℓ + νℓ branching fraction is measured to be (4.2 ± 1.1(stat.) ± 0.3(syst.)) × 10 –5 . For B + → η'ℓ + νℓ, we observe no significant signal and set an upper limit of 0.72 × 10 –4 at 90% confidence level.
72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
Polarization transfer observables in elastic electron-proton scattering at Q 2 = 2.5 , 5.2, 6.8, and 8.5 GeV 2
In this paper, interest in the behavior of nucleon electromagnetic form factors at large momentum transfers has steadily increased since the discovery, using polarization observables, of the rapid decrease of the ratio G p E /G p M of the proton's electric and magnetic form factors for momentum transfers Q 2 ≳ 1 GeV 2 , in strong disagreement with previous extractions of this ratio using the traditional Rosenbluth separation technique. The GEp-III and GEp-2$\gamma$ experiments were carried out in Jefferson Lab's (JLab's) Hall C from 2007-2008, to extend the knowledge of $G_E^p/G_M^p$ to the highest practically achievable $Q^2$ and to search for effects beyond the Born approximation in polarization transfer observables of elastic $\vec{e}p$ scattering. This article reports an expanded description of the common experimental apparatus and data analysis procedure, and the results of a final reanalysis of the data from both experiments, including the previously unpublished results of the full-acceptance data of the GEp-2$\gamma$ experiment. The Hall C High Momentum Spectrometer detected and measured the polarization of protons recoiling elastically from collisions of JLab's polarized electron beam with a liquid hydrogen target. A large-acceptance electromagnetic calorimeter detected the elastically scattered electrons in coincidence to suppress inelastic backgrounds. The final GEp-III data are largely unchanged relative to the originally published results. The statistical uncertainties of the final GEp-2$\gamma$ data are significantly reduced at $\epsilon = 0.632$ and $0.783$ relative to the original publication. The decrease with $Q^2$ of $G_E^p/G_M^p$ continues to $Q^2 = 8.5$ GeV$^2$, but at a slowing rate relative to the approximately linear decrease observed in earlier Hall A measurements. At $Q^2 = 2.5$ GeV$^2$, the proton form factor ratio $G_E^p/G_M^p$ shows no statistically significant $\epsilon$-dependence, as expected in the Born approximation. The ratio $P_\ell/P_\ell^{Born}$ of the longitudinal polarization transfer component to its Born value shows an enhancement of roughly 1.7\% at $\epsilon = 0.783$ relative to $\epsilon = 0.149$, with $\approx 2.2\sigma$ significance based on the total uncertainty, implying a similar effect in the transverse component $P_t$ that cancels in the ratio $R$.
73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
Tall Tower Vertical Profiles and Diurnal Trends of Ammonia in the Colorado Front Range: Tall Tower Vertical Profiles of Ammonia
Ammonia (NH 3 ) mixing ratios were measured between the surface and 280 m aboveground level from a moveable carriage at the Boulder Atmospheric Observatory tower in summer 2014 as part of the Front Range Air Pollution and Photochemistry Éxperiment. The campaign median mixing ratio was 3.3 ppb, ranging from below detection limits to 192 ppb. Median vertical profiles show an overall increase in NH 3 mixing ratios toward the surface of 6.7 ppb (89%) during the day and 3.9 ppb (141%) at night. In contrast to the overall increasing trend, some individual profiles show decreasing NH 3 in the lowest 10 m. This suggests that the local surface is capable of acting as either a source or a sink, depending on the relative amounts of NH 3 at the surface, and in advected air parcels. We further use this data set to investigate the variation in diurnal patterns of NH 3 as a function of height above the surface. At higher altitudes (100 ± 5 and 280 ± 5 m), NH 3 mixing ratios reach a gradual maximum during the day between 9:00 and 16:00 local time, likely driven by changes in source region. At lower altitudes (10 ± 5 m), the daytime maximum begins earlier at about 7:00 local time, followed by a sharper increase at 9:00 local time. At this height we also observe a peak in NH3 mixing ratios during the night, likely driven by the trapping of emitted NH 3 within the shallower nocturnal boundary layer.
54 ENVIRONMENTAL SCIENCES↗
Search for C P Violation and Measurement of the Branching Fraction in the Decay D 0 → K S 0 K S 0
In this work we study the decay D 0 → K S 0 K S 0 using 921 fb - 1 of data collected at or near the Υ ( 4 S ) and Υ ( 5 S ) resonances with the Belle detector at the KEKB asymmetric energy e + e - collider. The measured time-integrated C P asymmetry is A C P ( D 0 → K S 0 K S 0 ) = ( - 0.02 ± 1.53 ± 0.02 ± 0.17 ) % , and the branching fraction is B ( D 0 → K S 0 K S 0 ) = ( 1.321 ± 0.023 ± 0.036 ± 0.044 ) × 10 - 4 , where the first uncertainty is statistical, the second is systematic, and the third is due to the normalization mode ( D 0 → K S 0 π 0 ). These results are furthermore more precise than previous measurements available for this mode. The A C P measurement is consistent with the standard model expectation.
72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
Spectroscopic Observations of Magnetic Reconnection and Chromospheric Evaporation in an X-shaped Solar Flare
We present observations of distinct UV spectral properties at different locations during an atypical X-shaped flare (SOL2014-11-09T15:32) observed by the Interface Region Imaging Spectrograph ( IRIS ). In this flare, four chromospheric ribbons appear and converge at an X-point where a separator is anchored. Above the X-point, two sets of non-coplanar coronal loops approach laterally and reconnect at the separator. The IRIS slit was located close to the X-point, cutting across some of the flare ribbons and loops. Near the location of the separator, the Si iv 1402.77 Å line exhibits significantly broadened line wings extending to 200 km s{sup −1} with an unshifted line core. These spectral features suggest the presence of bidirectional flows possibly related to the separator reconnection. While at the flare ribbons, the hot Fe xxi 1354.08 Å line shows blueshifts and the cool Si iv 1402.77 Å, C ii 1335.71 Å, and Mg ii 2803.52 Å lines show evident redshifts up to a velocity of 80 km s{sup −1}, which are consistent with the scenario of chromospheric evaporation/condensation.
79 ASTRONOMY AND ASTROPHYSICS↗
Search for Λ c + → φ p π 0 and branching fraction measurement of Λ c + → K - π + p π 0
We have investigated the Cabibbo-suppressed decay Λ c + → φ p π 0 in e + e - collisions using a data sample corresponding to an integrated luminosity of 915 fb - 1 . The data were collected by the Belle experiment at the KEKB e + e - asymmetric-energy collider running at or near the Υ ( 4 S ) and Υ ( 5 S ) resonances. No significant signal is observed, and we set an upper limit on the branching fraction of B ( Λ c + → φ p π 0 ) < 15.3 × 10 - 5 at 90% confidence level. The contribution of nonresonant Λ c + → K + K - p π 0 decays is found to be consistent with zero, and the corresponding upper limit on its branching fraction is set to be B ( Λ c + → K + K - p π 0 ) NR < 6.3 × 10 - 5 at 90% confidence level. We also search for an intermediate hidden-strangeness pentaquark decay P s + → φ p . We see no evidence for this intermediate decay and set an upper limit on the product branching fraction of B ( Λ c + → P s + π 0 ) × B ( P s + → φ p ) < 8.3 × 10 - 5 at 90% confidence level. Finally, we measure the branching fraction for the Cabibbo-favored decay Λ c + → K - π + p π 0 ; the result is B ( Λ c + → K - π + p π 0 ) = ( 4.42 ± 0.05 ( stat ) ± 0.12 ( syst ) ± 0.16 ( norm ) ) % , which is the most decisive measurement to date.
72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
Probing Large-Scale Coherence Between Spitzer IR and Chandra X-Ray Source-Subtracted Cosmic Backgrounds
We present new measurements of the large-scale clustering component of the cross-power spectra of the source-subtracted Spitzer-IRAC cosmic infrared background and Chandra-ACIS cosmic X-ray background surface brightness fluctuations. Our investigation uses data from the Chandra Deep Field South, Hubble Deep Field North, Extended Groth Strip/AEGIS (All-wavelength Extended Groth Strip International Survey) field, and UDS (Ultra-Deep Survey) / SXDF surveys, comprising 1160 Spitzer hours and approximately 12 megaseconds of Chandra data collected over a total area of 0.3 degrees squared. We report the first (greater than 5 sigma) detection of a cross-power signal on large angular scales greater than 20 arc seconds between [0.5-2] kiloelectronvolts and the 3.6 and 4.5 micron bands, at approximately 5 omega and 6.3 sigma significance, respectively. The correlation with harder X-ray bands is marginally significant. Comparing the new observations with existing models for the contribution of the known unmasked source population at redshift less than 7, we find an excess of about an order of magnitude at 5 sigma confidence. We discuss possible interpretations for the origin of this excess in terms of the contribution from accreting early black holes (BHs), including both direct collapse BHs and primordial BHs, as well as from scattering in the interstellar medium and intra-halo light.
Capelluti, N.↗
Probing Large-scale Coherence between Spitzer IR and Chandra X-Ray Source-subtracted Cosmic Backgrounds
We present new measurements of the large-scale clustering component of the cross-power spectra of the source-subtracted Spitzer -IRAC cosmic infrared background and Chandra -ACIS cosmic X-ray background surface brightness fluctuations Our investigation uses data from the Chandra Deep Field South, Hubble Deep Field North, Extended Groth Strip/AEGIS field, and UDS/SXDF surveys, comprising 1160 Spitzer hours and ∼12 Ms of Chandra data collected over a total area of 0.3 deg{sup 2}. We report the first (>5 σ ) detection of a cross-power signal on large angular scales >20″ between [0.5–2] keV and the 3.6 and 4.5 μ m bands, at ∼5 σ and 6.3 σ significance, respectively. The correlation with harder X-ray bands is marginally significant. Comparing the new observations with existing models for the contribution of the known unmasked source population at z < 7, we find an excess of about an order of magnitude at 5 σ confidence. We discuss possible interpretations for the origin of this excess in terms of the contribution from accreting early black holes (BHs), including both direct collapse BHs and primordial BHs, as well as from scattering in the interstellar medium and intra-halo light.
79 ASTRONOMY AND ASTROPHYSICS↗
Measurement of the branching fraction and C P asymmetry in B 0 → π 0 π 0 decays, and an improved constraint on φ 2
Here, we measure the branching fraction and C P violation asymmetry in the decay B 0 → π 0 π 0 , using a data sample of 752 × 10 6 B B ¯ pairs collected at the Υ ( 4 S ) resonance with the Belle detector at the KEKB e + e - collider. The obtained branching fraction and direct C P asymmetry are B ( B → π 0 π 0 ) = [ 1.31 ± 0.19 ( stat ) ± 0.19 ( syst ) ] × 10 - 6 and A C P = + 0.14 ± 0.36 ( stat ) ± 0.10 ( syst ) , respectively. The signal significance, including the systematic uncertainty, is 6.4 standard deviations. Furthemore, we combine these results with Belle’s earlier measurements of B 0 → π + π - and B ± → π ± π 0 to exclude the C P -violating parameter φ 2 from the range 15.5 ° < φ 2 < 75.0 ° at 95% confidence level.
72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
Noise Characterization and Filtering in the MicroBooNE Liquid Argon TPC
The low-noise operation of readout electronics in a liquid argon time projection chamber (LArTPC) is critical to properly extract the distribution of ionization charge deposited on the wire planes of the TPC, especially for the induction planes. This paper describes the characteristics and mitigation of the observed noise in the MicroBooNE detector. The MicroBooNE's single-phase LArTPC comprises two induction planes and one collection sense wire plane with a total of 8256 wires. Current induced on each TPC wire is amplified and shaped by custom low-power, low-noise ASICs immersed in the liquid argon. The digitization of the signal waveform occurs outside the cryostat. Using data from the first year of MicroBooNE operations, several excess noise sources in the TPC were identified and mitigated. The residual equivalent noise charge (ENC) after noise filtering varies with wire length and is found to be below 400 electrons for the longest wires (4.7 m). The response is consistent with the cold electronics design expectations and is found to be stable with time and uniform over the functioning channels. This noise level is significantly lower than previous experiments utilizing warm front-end electronics.
46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗