Ahmed Ali

Bio: Ahmed Ali is an academic researcher from Taif University. The author has contributed to research in topics: Medicine & Computer science. The author has an hindex of 61, co-authored 728 publications receiving 15197 citations. Previous affiliations of Ahmed Ali include Université de Sherbrooke & University of Baghdad.

TESLA Technical Design Report Part III: Physics at an e+e- Linear Collider

Abstract: The TESLA Technical Design Report Part III: Physics at an e+e- Linear Collider

Experimental tests of factorization in charmless nonleptonic two-body B decays

Abstract: Using a theoretical framework based on the next-to-leading-order QCD-improved effective Hamiltonian and a factorization ansatz for the hadronic matrix elements of the four-quark operators, we reassess branching fractions in two-body nonleptonic decays $\stackrel{\ensuremath{\rightarrow}}{B}PP,PV,VV,$ involving the lowest-lying light pseudoscalar $(P)$ and vector $(V)$ mesons in the standard model. We work out the parametric dependence of the decay rates, making use of the currently available information on the weak mixing matrix elements, form factors, decay constants, and quark masses. Using the sensitivity of the decay rates on the effective number of colors, ${N}_{c},$ as a criterion of theoretical predictivity, we classify all the current-current (tree) and penguin transitions in five different classes. The recently measured charmless two-body $\stackrel{\ensuremath{\rightarrow}}{B}\mathrm{PP}$ decays ${(B}^{+}\ensuremath{\rightarrow}{K}^{+}{\ensuremath{\eta}}^{\ensuremath{'}}, {B}^{0}\ensuremath{\rightarrow}{K}^{0}{\ensuremath{\eta}}^{\ensuremath{'}}, {B}^{0}\ensuremath{\rightarrow}{K}^{+}{\ensuremath{\pi}}^{\ensuremath{-}}, {B}^{+}\ensuremath{\rightarrow}{\ensuremath{\pi}}^{+}{K}^{0},$ and charge conjugates) are dominated by the ${N}_{c}$-stable QCD penguin transitions (class-IV transitions) and their estimates are consistent with the data. The measured charmless $\stackrel{\ensuremath{\rightarrow}}{B}\mathrm{PV} {(B}^{+}\ensuremath{\rightarrow}\ensuremath{\omega}{K}^{+}, {B}^{+}\ensuremath{\rightarrow}\ensuremath{\omega}{h}^{+})$ and $\stackrel{\ensuremath{\rightarrow}}{B}\mathrm{VV}$ transition $(\stackrel{\ensuremath{\rightarrow}}{B}\ensuremath{\varphi}{K}^{*}),$ on the other hand, belong to the penguin (class-V) and tree (class-III) transitions. The class-V penguin transitions are ${N}_{c}$ sensitive and/or involve large cancellations among competing amplitudes, making their decay rates in general more difficult to predict. Some of these transitions may also receive significant contributions from annihilation and/or final state interactions. We propose a number of tests of the factorization framework in terms of the ratios of branching ratios for some selected $\stackrel{\ensuremath{\rightarrow}}{B}{h}_{1}{h}_{2}$ decays involving light hadrons ${h}_{1}$ and ${h}_{2},$ which depend only moderately on the form factors. We also propose a set of measurements to determine the effective coefficients of the current-current and QCD penguin operators. The potential impact of $\stackrel{\ensuremath{\rightarrow}}{B}{h}_{1}{h}_{2}$ decays on the CKM phenomenology is emphasized by analyzing a number of decay rates in the factorization framework.

A Comparative study of the decays $B \to$ ($K$, $K^{*)} \ell^+ \ell^-$ in standard model and supersymmetric theories

Abstract: Using improved theoretical calculations of the decay form factors in the Light Cone-QCD sum rule approach, we investigate the decay rates, dilepton invariant mass spectra and the forward-backward (FB) asymmetry in the decays B → (K, K ∗ )l + l − (l ± = e ± , µ ± , τ ± ) in the standard model (SM) and a number of popular variants of the supersymmetric (SUSY) models. Theoretical precision on the differential decay rates and FB-asymmetry is estimated in these theories taking into account various parametric uncertainties. We show that existing data on B → Xsγ and the experimental upper limit on the branching ratio B(B → K ∗ µ + µ − ) provide interesting bounds on the coefficients of the underlying effective theory. We argue that the FB-asymmetry in B → K ∗ l + l − constitutes a precision test of the SM and its measurement in forthcoming experiments may reveal new physics. In particular, the presently allowed largetan β solutions in SUGRA models, as well as more general flavor-violating SUSY models, yield FB-asymmetries which are characteristically different from the corresponding ones in the SM.

Constraint on the matter–antimatter symmetry-violating phase in neutrino oscillations

Abstract: The charge-conjugation and parity-reversal (CP) symmetry of fundamental particles is a symmetry between matter and antimatter. Violation of this CP symmetry was first observed in 19641, and CP violation in the weak interactions of quarks was soon established2. Sakharov proposed3 that CP violation is necessary to explain the observed imbalance of matter and antimatter abundance in the Universe. However, CP violation in quarks is too small to support this explanation. So far, CP violation has not been observed in non-quark elementary particle systems. It has been shown that CP violation in leptons could generate the matter–antimatter disparity through a process called leptogenesis4. Leptonic mixing, which appears in the standard model’s charged current interactions5,6, provides a potential source of CP violation through a complex phase δCP, which is required by some theoretical models of leptogenesis7,8,9. This CP violation can be measured in muon neutrino to electron neutrino oscillations and the corresponding antineutrino oscillations, which are experimentally accessible using accelerator-produced beams as established by the Tokai-to-Kamioka (T2K) and NOvA experiments10,11. Until now, the value of δCP has not been substantially constrained by neutrino oscillation experiments. Here we report a measurement using long-baseline neutrino and antineutrino oscillations observed by the T2K experiment that shows a large increase in the neutrino oscillation probability, excluding values of δCP that result in a large increase in the observed antineutrino oscillation probability at three standard deviations (3σ). The 3σ confidence interval for δCP, which is cyclic and repeats every 2π, is [−3.41, −0.03] for the so-called normal mass ordering and [−2.54, −0.32] for the inverted mass ordering. Our results indicate CP violation in leptons and our method enables sensitive searches for matter–antimatter asymmetry in neutrino oscillations using accelerator-produced neutrino beams. Future measurements with larger datasets will test whether leptonic CP violation is larger than the CP violation in quarks.

Phd by thesis

Abstract: Deposits of clastic carbonate-dominated (calciclastic) sedimentary slope systems in the rock record have been identified mostly as linearly-consistent carbonate apron deposits, even though most ancient clastic carbonate slope deposits fit the submarine fan systems better. Calciclastic submarine fans are consequently rarely described and are poorly understood. Subsequently, very little is known especially in mud-dominated calciclastic submarine fan systems. Presented in this study are a sedimentological core and petrographic characterisation of samples from eleven boreholes from the Lower Carboniferous of Bowland Basin (Northwest England) that reveals a >250 m thick calciturbidite complex deposited in a calciclastic submarine fan setting. Seven facies are recognised from core and thin section characterisation and are grouped into three carbonate turbidite sequences. They include: 1) Calciturbidites, comprising mostly of highto low-density, wavy-laminated bioclast-rich facies; 2) low-density densite mudstones which are characterised by planar laminated and unlaminated muddominated facies; and 3) Calcidebrites which are muddy or hyper-concentrated debrisflow deposits occurring as poorly-sorted, chaotic, mud-supported floatstones. These

PYTHIA 6.4 Physics and Manual

Abstract: The Pythia program can be used to generate high-energy-physics ''events'', i.e. sets of outgoing particles produced in the interactions between two incoming particles. The objective is to provide as accurate as possible a representation of event properties in a wide range of reactions, within and beyond the Standard Model, with emphasis on those where strong interactions play a role, directly or indirectly, and therefore multihadronic final states are produced. The physics is then not understood well enough to give an exact description; instead the program has to be based on a combination of analytical results and various QCD-based models. This physics input is summarized here, for areas such as hard subprocesses, initial- and final-state parton showers, underlying events and beam remnants, fragmentation and decays, and much more. Furthermore, extensive information is provided on all program elements: subroutines and functions, switches and parameters, and particle and process data. This should allow the user to tailor the generation task to the topics of interest.