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Ahmed, H.

Publications and source records attributed to Ahmed, H..

At least 19 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2022

Combined analysis of Belle and Belle II data to determine the CKM angle φ 3 using B + → D($ {K}_S^0 $h + h – )h + decays

We present a measurement of the Cabibbo-Kobayashi-Maskawa unitarity triangle angle φ 3 (also known as γ) using a model-independent Dalitz plot analysis of B + → D($ {K}_S^0 $h + h – )h + , where D is either a D o or D o ¯ meson and h is either a π or K. This is the first measurement that simultaneously uses Belle and Belle II data, combining samples corresponding to integrated luminosities of 711 fb –1 and 128 fb –1 , respectively. All data were accumulated from energy-asymmetric e + e – collisions at a centre-of-mass energy corresponding to the mass of the Υ(4S) resonance. We measure φ 3 = (78.4 ± 11.4 ± 0.5 ± 1.0)°, where the first uncertainty is statistical, the second is the experimental systematic uncertainty and the third is from the uncertainties on external measurements of the D-decay strong-phase parameters.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2019

Developing the Oxidation Kinetic Model for Magnetite Pellet

Oxidation is a vital phenomenon for magnetite pellets in their excursion through the furnace during induration. One of the pre-requisites for magnetite pellets to achieve homogeneously structured good quality pellets is to have complete oxidation before sintering begins. Partially oxidized magnetite pellets, upon sintering, might result in inhomogeneous structured pellets which could be detrimental to pellet quality. It is necessary to understand the mechanisms responsible for magnetite oxidation, and hence, it is intended in this study to investigate experimentally as well as develop a mathematical model based on oxidation kinetics. Oxidation of pellets is largely influenced by the oxidation kinetics of particles and hence should be studied at particle as well as at pellet scale. The principles of the Grain Model have been adopted to develop the Oxidation Model at pellet scale, whereas the particles’ oxidation follows the Avrami Kinetic Model. Isothermal oxidation experiments performed Thermogravimetric Analyzer showed that oxidation rate of magnetite at pellet scale contained two peaks. They were complemented well by oxidation rates predicted from the model. Further, the pellet was investigated microstructurally at pellet and particle scale to substantiate the findings from the experiments and the model. The oxidation model developed is used to predict the progression of oxidation in the magnetite pellet with respect to the reaction time at three different temperatures (873 K, 973 K, and 1073 K (600 °C, 700 °C, and 800 °C)) and at four levels of oxygen (0.21, 0.30, 0.60, and 1.00 atm) in the oxidizing gas.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Investigation of Magnetite Oxidation Kinetics at the Particle Scale

The induration of magnetite pellets is a complex physico-chemical process that involves oxidation, sintering, and heat transfer. The thermal- and gas-composition profile that is experienced by the pellet in an induration reactor could result in the formation of a homogenous or heterogeneous pellet structure, which could affect the pellet quality. The oxidation kinetics of magnetite pellets from sintering studies have been studied at two levels, namely, the pellet scale and at the particle scale, and the findings of the latter are presented here. The rate of oxidation of the magnetite concentrate depends primarily on temperature, oxygen content in the oxidizing gas, and particle size. These factors are investigated in this study. It was found that the oxidation of the magnetite concentrate is comprised of two distinct stages, a primary stage with high rates followed by a secondary stage where rates decrease significantly. The isothermal oxidation behavior as analyzed by the Avrami kinetic model was found to fit better than the shrinking-core model. The partially oxidized particles were examined microstructurally to supplement the experimental and model results. The Avrami kinetic model for isothermal oxidation was extended to non-isothermal profiles using the superposition principle, and the model was validated experimentally.

36 MATERIALS SCIENCE↗
DOE OSTI2017

Measurement of the e + e - → π + π - π 0 π 0 cross section using initial-state radiation at BABAR

Here, the process e + e – →π + π – 2π 0 γ is investigated by means of the initial-state radiation technique, where a photon is emitted from the incoming electron or positron. Using 454.3 fb –1 of data collected around a center-of-mass energy of √s=10.58 GeV by the BABAR experiment at SLAC, approximately 150000 signal events are obtained. The corresponding nonradiative cross section is measured with a relative uncertainty of 3.6% in the energy region around 1.5 GeV, surpassing all existing measurements in precision. Using this new result, the channel’s contribution to the leading order hadronic vacuum polarization contribution to the anomalous magnetic moment of the muon is calculated as (gπ + π – 2π 0 μ –2)/2=(17.9 ± 0.1 stat ± 0.6 syst )×10–10 in the energy range 0.85 GeV < E CM < 1.8 GeV. In the same energy range, the impact on the running of the fine-structure constant at the Z 0 -pole is determined as Δαπ + π – 2π 0 (M 2 Z )=(4.44 ± 0.02 stat ± 0.14 syst ) × 10 –4 . Furthermore, intermediate resonances are studied and especially the cross section of the process e + e – →ωπ 0 →π + π – 2π 0 is measured.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2017

Measurement of the D * ( 2010 ) + - D + Mass Difference

Here, we measure the mass difference, Δm + , between the D* (2010) + and the D + using the decay chain D* (2010) + → D + π 0 with D + → K - π + π + . The data were recorded with the BABAR detector at center-of-mass energies at and near the Υ(4S) resonance, and correspond to an integrated luminosity of approximately 468 fb -1 . We measure Δm + = (140 601.0 ± 6.8 [stat] ± 12.9 [syst] ) keV . We combine this result with a previous BABAR measurement of Δm 0 ≡ m(D* (2010) + ) - m (D 0 ) to obtain Δm D = m (D + ) - m (D 0 ) = ( 4824.9 ± 6.8 [stat] ± 12.9 [syst]) keV . These results are compatible with and approximately five times more precise than the Particle Data Group averages.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2017

Time evolution and asymmetry of a laser produced blast wave

Studies of a blast wave produced from carbon rods and plastic spheres in an argon background gas have been conducted using the Vulcan laser at the Rutherford Appleton Laboratory. A laser of 1500 J was focused onto these targets, and rear-side observations of an emission front were recorded using a fast-framing camera. The emission front is asymmetrical in shape and tends to a more symmetrical shape as it progresses due to the production of a second shock wave later in time, which pushes out the front of the blast wave. Plastic spheres produce faster blast waves, and the breakthrough of the second shock is visible before the shock stalls. The results are presented to demonstrate this trend, and similar evolution dynamics of experimental and simulation data from the FLASH radiation-hydrodynamics code are observed.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2017

Measurement of the e + e - → K s 0 K ± π ∓ π 0 and K s 0 K ± π ∓ η cross sections using initial-state radiation

The processes e + e - → K$0\atop{S}$ K ± π ∓ π 0 and e + e - → K$0\atop{S}$ K ± π ∓ η are studied over a continuum of energies from threshold to 4 GeV with the initial-state photon radiation method. Using 454 fb -1 of data collected with the BABAR detector at the SLAC PEP-II storage ring, the first measurements of the cross sections for these processes are obtained. The intermediate resonance structures from K* 0 (Kπ) 0 , K *(892) ± (Kπ) ∓ , and K$0\atop{S}$K ± ρ ∓ are studied. Lastly, the J / ψ is observed in all of these channels, and corresponding branching fractions are measured.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2017

Dalitz plot analyses of J / ψ → π + π - π 0 , J / ψ → K + K - π 0 , and J / ψ → K s 0 K ± π ∓ produced via e + e - annihilation with initial-state radiation

Here, we study the processes e + e - → γ ISR J/ψ , where J/ψ → π + π - π 0 , J/ψ → K + K - π 0 , and J / ψ → K$0\atop{S}$ K ± π ∓ using a data sample of 519 fb -1 recorded with the BABAR detector operating at the SLAC PEP-II asymmetric-energy e + e - collider at center-of-mass energies at and near the Υ (nS) (n = 2 , 3 , 4) resonances. We measure the ratio of branching fractions R 1 = $B(J/ψ →K^+K^- π^0)\atop{B(J/ψ →π^+π^- π^0)}$ and R 2 = $B(J/ψ →K^0_SK^±π^∓)\atop{B(J/ψ →π^+π^- π^0)}$. We perform Dalitz plot analyses of the three J/ψ decay modes and measure fractions for resonances contributing to the decays. We also analyze the J/ψ → $π^+π^- π^0$ decay using the Veneziano model. We observe structures compatible with the presence of ρ (1450) in all three J/ψ decay modes and measure the relative branching fraction: R (p(1450)) = $Bp(1450)→K^+K^-)\atop{B(p(1450)→π^+π^-)}$ +0.307 ± 0.084 (stat) ± 0.082 (sys).

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2017

Measurement of the inclusive electron spectrum from B meson decays and determination of | V u b |

Based on the full BABAR data sample of 466.5 million $B\bar{B}$ pairs, we present measurements of the electron spectrum from semileptonic B meson decays. We fit the inclusive electron spectrum to distinguish Cabibbo-Kobayashi-Maskawa (CKM) suppressed B → X u eν decays from the CKM-favored B → X c eν decays, and from various other backgrounds, and determine the total semileptonic branching fraction B (B → Xeν) = ( 10.34 ± 0.04 stat ± 0.2 6 syst )%, averaged over B ± and B 0 mesons. We determine the spectrum and branching fraction for charmless B → X u eν decays and extract the CKM element | V ub | , by relying on four different QCD calculations based on the heavy quark expansion. While experimentally, the electron momentum region above 2.1 GeV / c is favored, because the background is relatively low, the uncertainties for the theoretical predictions are largest in the region near the kinematic endpoint. Detailed studies to assess the impact of these four predictions on the measurements of the electron spectrum, the branching fraction, and the extraction of the CKM matrix element |V ub | are presented, with the lower limit on the electron momentum varied from 0.8 GeV / c to the kinematic endpoint. We determine |V ub | using each of these different calculations and find, |V ub | = ( 3.794 ± 0.107 exp $+ 0.292\atop{ - 0.219 SF}$ $+ 0.078 \atop{- 0.068 theory}$ ) × 10 - 3 (De Fazio and Neubert), (4.563 ± 0.126 exp $+ 0.230\atop {- 0.208 SF}$ $+ 0.162\atop{- 0.163 theory}$ ) ×10 -3 (Bosch, Lange, Neubert, and Paz), (3.959 ± 0.104 exp $+ 0.164\atop{- 0.154 SF}$ $+ 0.042\atop{ - 0.079 theory}$ ) × 10 -3 (Gambino, Giordano, Ossola, and Uraltsev), (3.848 ± 0.108 exp $+ 0.084\atop{ - 0.070 theory}$) × 10 -3 (dressed gluon exponentiation), where the stated uncertainties refer to the experimental uncertainties of the partial branching fraction measurement, the shape function parameters, and the theoretical calculations.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2017

Cross sections for the reactions e + e - → K S 0 K L 0 π 0 , K S 0 K L 0 η , and K S 0 K L 0 π 0 π 0 from events with initial-state radiation

Here, we study the processes e + e - → K$0\atop{S}$ K$0\atop{L}$ π 0 γ , K $0\atop{S}$ K$0\atop{L}$ η γ , and K$0\atop{S}$ K$0\atop{L}$ π 0 π 0 γ , where the photon is radiated from the initial state, providing cross section measurements for the hadronic final states over a continuum of center-of-mass energies. The results are based on 469 fb -1 of data collected at or near the Υ ( 4 S ) resonance with the BABAR detector at SLAC. We present the first measurements of the e + e - → K$0\atop{S}$ K$0\atop{L}$ π 0 , K$0\atop{S}$ K$0\atop{L}$ η , and K$0\atop{S}$ K$0\atop{L}$ π 0 π 0 cross sections up to a center-of-mass energy of 4 GeV and study their intermediate resonance structures. We observe J / ψ decays to all of these final states for the first time, present measurements of their J / ψ branching fractions, and search for ψ (2S) decays.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2017

Search for B + → K + τ + τ - at the BaBar Experiment

We search for the rare flavor-changing neutral current process B + → K + τ + τ - using data from the BABAR experiment. The data sample, collected at the center-of-mass energy of the Υ ( 4 S ) resonance, corresponds to a total integrated luminosity of 424 fb - 1 and to 471 × 1 0 6 B$\bar{B}$ pairs. We reconstruct one B meson, produced in the Υ ( 4 S ) → B + B - decay, in one of many hadronic decay modes and search for activity compatible with a B + → K + τ + τ - decay in the rest of the event. Each τ lepton is required to decay leptonically into an electron or muon and neutrinos. Comparing the expected number of background events with the data sample after applying the selection criteria, we do not find evidence for a signal. The resulting upper limit, at the 90% confidence level, is B ( B + → K + τ + τ - ) < 2.25 × 10 - 3 .

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2017

Experimental Observation of Thin-shell Instability in a Collisionless Plasma

We report on the experimental observation of the instability of a plasma shell, which formed during the expansion of a laser-ablated plasma into a rarefied ambient medium. By means of a proton radiography technique, the evolution of the instability is temporally and spatially resolved on a timescale much shorter than the hydrodynamic one. The density of the thin shell exceeds that of the surrounding plasma, which lets electrons diffuse outward. An ambipolar electric field grows on both sides of the thin shell that is antiparallel to the density gradient. Ripples in the thin shell result in a spatially varying balance between the thermal pressure force mediated by this field and the ram pressure force that is exerted on it by the inflowing plasma. This mismatch amplifies the ripples by the same mechanism that drives the hydrodynamic nonlinear thin-shell instability (NTSI). Our results thus constitute the first experimental verification that the NTSI can develop in colliding flows.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2016

Measurement of the B 0 → D * - π + π - π + branching fraction

When using a sample of ( 470.9 ± 2.8 ) × 10 6 B$\bar{B}$ pairs, we measure the decay branching fraction B ( B 0 → D * - π + π - π + ) = ( 7.26 ± 0.11 ± 0.31 ) × 10 -3 , where the first uncertainty is statistical and the second is systematic. These measurement will be helpful in studies of lepton universality by measuring B ( B 0 → D * - τ + ν τ ) using τ + → π + π - π + ¯ ν τ decays, normalized to B ( B 0 → D * - π + π - π + ) .

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗