A Geometric Parametrization of the Cabibbo-Kobayashi-Maskawa Matrix and the Jarlskog Invariant

In this paper we give a geometric parametrization to the Cabibbo-Kobayashi-Maskawa (CKM) mixing matrix and the Jarlskog invariant, which is based on two flag manifolds $SU(3)/U(1)^{2}$. To treat a fourth generation of quarks on CP violation we generalize the parametrization to one based on two flag manifolds $SU(4)/U(1)^{3}$.Comment: Latex ; 14 pages ; 2 figures ; minor change

Timing and correction of stepping movements with a virtual reality avatar

Research into the ability to coordinate one’s movements with external cues has focussed on the use of simple rhythmic, auditory and visual stimuli, or interpersonal coordination with another person. Coordinating movements with a virtual avatar has not been explored, in the context of responses to temporal cues. To determine whether cueing of movements using a virtual avatar is effective, people’s ability to accurately coordinate with the stimuli needs to be investigated. Here we focus on temporal cues, as we know from timing studies that visual cues can be difficult to follow in the timing context. Real stepping movements were mapped onto an avatar using motion capture data. Healthy participants were then motion captured whilst stepping in time with the avatar’s movements, as viewed through a virtual reality headset. The timing of one of the avatar step cycles was accelerated or decelerated by 15% to create a temporal perturbation, for which participants would need to correct to, in order to remain in time. Step onset times of participants relative to the corresponding step-onsets of the avatar were used to measure the timing errors (asynchronies) between them. Participants completed either a visual-only condition, or auditory-visual with footstep sounds included, at two stepping tempo conditions (Fast: 400ms interval, Slow: 800ms interval). Participants’ asynchronies exhibited slow drift in the Visual-Only condition, but became stable in the Auditory-Visual condition. Moreover, we observed a clear corrective response to the phase perturbation in both the fast and slow tempo auditory-visual conditions. We conclude that an avatar’s movements can be used to influence a person’s own motion, but should include relevant auditory cues congruent with the movement to ensure a suitable level of entrainment is achieved. This approach has applications in physiotherapy, where virtual avatars present an opportunity to provide the guidance to assist patients in adhering to prescribed exercises

Cosmological implications of conformal field theory

Requiring all massless elementary fields to have conformal scaling symmetry removes a conflict between gravitational theory and the quantum theory of elementary particles and fields. Extending this postulate to the scalar field of the Higgs model, dynamical breaking of both gauge and conformal symmetries determines parameters for the interacting fields. In uniform isotropic geometry a modified Friedmann cosmic evolution equation is derived with nonvanishing cosmological constant. Parameters determined by numerical solution are consistent with empirical data for redshifts $z\leq z_*=1090$, including luminosity distances for observed type Ia supernovae and peak structure ratios in the cosmic microwave background (CMB). The theory does not require dark matter.Comment: 8 pages Conclusions about the early universe which must be reexamined have been removed. Manuscript revised and reformatted. Accepted for publication in Modern Physics Letters A (2011

Possible Cosmological Implications of the Quark-Hadron Phase Transition

We study the quark-hadron phase transition within an effective model of QCD, and find that in a reasonable range of the main parameters of the model, bodies with quark content between $10^{-2}$ and 10 solar masses can have been formed in the early universe. In addition, we show that a significant amount of entropy is released during the transition. This may imply the existence of a higher baryon number density than what is usually expected at temperatures above the QCD scale. The cosmological QCD transition may then provide a natural way for decreasing the high baryon asymmetry created by an Affleck-Dine like mechanism down to the value required by primordial nucleosynthesis.Comment: 19 pages, LaTeX, 5 Postscript figures included. Submitted to Journal of Physics

Gluon and gluino penguin diagrams and the charmless decays of the b quark

Gluon mediated exclusive hadronic decays of b quarks are studied within the standard model (SM) and the constrained minimally supersymmetric standard model (MSSM). For all allowed regions of the MSSM parameter space (A, tan beta, m_0, m_{1/2}) the penguin magnetic dipole form factor F^R_2 is dominant over the electric dipole and can be larger than the magnetic dipole form factor of the SM. However, overall the SM electric dipole decay amplitude F^L_1 dominates the decay rate. The MSSM penguin contributions to the free quark decay rate approach the 10% level for those regions of parameter space close to the highest allowed values of tan beta (~55) for which the gluino is light (m_{\tilde{g}} \approx 360 GeV) and lies within the range of the six d-squark masses. In these regions the supersymmetric box amplitudes are negligible. The MSSM phases change very little over the allowed parameter space and can lead to significant interference with the SM amplitudes

Factorization fits to charmless strangeless B decays

We present fits to charmless strangeless hadronic B decay data for mean branching ratios and CP-violating asymmetries using the QCD factorization model of Beneke et al. Apart from one CP-violating parameter, the model gives a very good representation of 26 measured data. We find the CKM angle alpha = (93.5 +/- 8.4 -1.3) degrees and to be quite stable to plausible "charming penguin" corrections.Comment: 4 pages, LaTeX, Minor changes to text, references adde

LHCb's Potential to Measure Flavour-Specific CP-Asymmetry in Semileptonic and Hadronic Bs0B^0_s Decays

"The CP asymmetry in Bs-Bsbar mixing, denoted as a^s_{fs}, is sensitive to new weak phases in the presence of physics beyond the Standard Model. This can be probed through a measurement of the time-dependent charge asymmetry A^s_{fs}(t) in flavour-specific decays. This note describes the LHCb strategy to measure a^s_{fs} using a time-dependent method, in flavour untagged decays of Bs->Ds mu nu and Bs->Ds pi. We also investigate a measurement of the difference of a^s_{fs} and a^d_{fs} in Bs->Ds mu nu and Bd->Dmu nu decays which allows to control the systematic uncertainty that arise from detection asymmetries.