118710048
Probing the fourth generation Majorana neutrino dark matter
The heavy fourth-generation Majorana neutrino can be stable and contribute to a small fraction of the relic density of dark matter (DM) in the Universe. Because of its strong coupling to the standard model particles, it can be probed by the current direct and indirect DM detection experiments even it is a subdominant component of the whole halo DM. Assuming that it contributes to the same fraction of the local halo DM density as that of the DM relic density in the Universe, we show that the current Xenon100 data constrain the mass of the stable Majorana neutrino to be greater than the mass of the top quark. In the mass range from 200 GeV to a few hundred GeV, the effective spin-independent cross section for the neutrino elastic-scattering off nucleon is insensitive to the neutrino mass and mixing, and is predicted to be similar to 1.5 X 10(-44) cm(2), which can be reached by the direct DM detection experiments soon. In the same mass region the predicted effective spin-dependent cross section for the heavy neutrino scattering off proton is in the range of 2 X 10(-40) cm(2) similar to 2 X 10(-39) cm(2), which is within the reach of the ongoing DM indirect search experiments such as IceCube. We demonstrate such properties of the heavy neutrino DM in a fourth-generation model with the stability of the fourth Majorana neutrino protected by an additional generation-dependent U(1) gauge symmetry.
119061151
Weak phase gamma and strong phase delta from CP averaged B ->pi pi and pi K decays
Assuming SU(3) symmetry for the strong phases in the four decay modes B-->pi(-)pi(+), pi(0)pi(+), pi(-)K(+), pi(-)(K) over bar(0) and ignoring the relative small electroweak penguin effects in those decays, the weak phase gamma and the strong phase delta can be determined in a model independent way by the CP averaged branching ratios of the four decay modes. It appears that the current experimental data for B-->pi pi and pi K decays prefer a negative value of cos gamma cos delta. By combining with the other constraints from V-ub B-d,s(0)-(B) over bar(d,s)(0) mixing, and the indirect CP-violating parameter epsilon(K) within the standard model, two favorable solutions for the phases gamma and delta are found to lie in the region 35 degrees less than or similar to gamma less than or similar to 62 degrees and 106 degrees less than or similar to delta less than or similar to 180 degrees or 86 degrees less than or similar to gamma less than or similar to 151 degrees and 0 degrees less than or similar to delta less than or similar to 75 degrees within 1 sigma standard deviation. It is noted that if allowing the standard deviation of the data to be more than 1 sigma, the two solutions could approach one solution with a much larger region for the phases gamma and delta. Direct CP asymmetry a(epsilon")((pi-K+)) in B -->pi(-)K(+) decay can be as large as the present experimental upper bound. Direct CP asymmetry a(epsilon")((pi+)pi-) in B-->pi(-)pi(+) decay can reach up to about 40% at the 1 sigma level.
27463348
Implications of new data in charmless B decays
Based on the latest experimental data of B ->pi pi and pi K modes, a model-independent analytical analysis is presented. The CP-averaged branching ratio difference Delta R=R-c-R-n in B ->pi K decays with R-c=2Br(pi K-0(-))/Br(pi(-)(K) over bar (0)) and R-n=Br(pi K-+(-))/2Br(pi(0)(K) over bar (0)) is reduced though it remains larger than the prediction from the standard model (SM) as both measured R-n and R-c are enhanced, which indicates that a room for new physics becomes smaller. The present data of pi pi decay reduce the ratio vertical bar C/T vertical bar from the previous value of vertical bar C/T vertical bar similar or equal to 0.8 to vertical bar C/T vertical bar similar or equal to 0.65, which is still larger than the theoretical estimations based on QCD factorization and pQCD. Within SM and flavor SU(3) symmetry, the current pi K data also diminish the ratio vertical bar C/T-'vertical bar from the previous value vertical bar C'/T'vertical bar similar or equal to 2 to vertical bar C'/T'vertical bar similar or equal to 1.16 with a large strong phase delta(C)'similar or equal to-2.65, while its value remains much larger than the one extracted from the pi pi modes. The direct CP violation A(CP)(pi(0)(K) over bar (0)) is predicted to be A(CP)(pi(0)(K) over bar (0))=-0.15 +/- 0.03, which is consistent with the present data. Two kinds of new effects in both strong and weak phases of the electroweak penguin diagram are considered. It is found that both cases can reduce the ratio to vertical bar C'/T'vertical bar=0.40 similar to 0.80 and lead to roughly the same predictions for CP violation in pi K-0(0).
115775190
More precise determination of V-cb & V-ub and direct CP violation in charmless B decays
More precise extractions on the two important CKM matrix elements \V-cb\ and \V-ub\ are presented up to 1/m(Q)(2) corrections, based on the complete heavy-quark effective field theory (HQEFT) of QCD. The HQEFT as a large component QCD provides us with a complete theoretical framework for correctly and systematically evaluating the subleading and higher-order contributions in 1/m(Q) expansion of heavy quarks. A global analysis on charmless B decays is made, based on the isospin and SU(3) flavor symmetry. An isospin relation is found to be very useful for studying SU(3) symmetry-breaking effects of strong phases and exploring new types of electroweak penguin effects. The direct CP violation in charmless B decays is predicted, and its precise measurement is helpful either for testing SU(3) symmetry breaking effects of strong phases or for probing news physics beyond standard model.
18105043
Chiral couplings of W ′ and top quark polarization at the LHC
If a TeV-scale charged gauge boson (W') is discovered at the Large Hadron Collider (LHC), it will become imperative to determine its chiral couplings to standard model (SM) fermions in order to learn about the underlying theory containing the W'. We describe the reconstruction of the tb decay mode of the W' at the LHC, and identify various kinematic observables such as the angular distributions of the top quark and the lepton resulting from top decay that can be used to disentangle the chiral couplings of the W' to SM fermions. We demonstrate by presenting analytical expressions, numerical simulations, as well as intuitive illustrations for these observables at the LHC that among the SM fermions, the polarized top quark can most directly probe the chirality of such couplings.
123787607
The Contribution of Reggeon in charge exchange processes
We discuss in this paper The experimental results on maximum psedo-rapidity $\eta_{max}$ distribution in the charge exchange process $e+p\to e+n+X$ in ZEUS Collaboration at HERA. We calculate the contributions of \regg ($\rho$-Reggeon associated with $\rho$ meson) from regge phenomenology and $\pi^{+}$-exchange from pion cloud model. The results show that neither the \regg-exchange nor the pion cloud model alone can explain the experimental data well, but after considering both these two processes together, by using Monte Carlo simulation, a good agreement between theoretical results and experimental data is found. This means that in discussing the large rapidity gap phenomena in deep inelastic scattering, both of the two processes play substantial role.
119117650
Anisotropic flow of identified particles in Pb--Pb collisions at $\sqrt{s_{_{\rm NN}}} =$ 2.76 TeV with the ALICE detector
The measurement of anisotropic flow of identified particles, including charged pion, kaon, (anti-)proton as well as strange and multi-strange particles (${\rm K_{S}^{0}}$, ${\rm \Lambda}$, ${\rm \Xi}$ and ${\rm \Omega}$) are measured in Pb--Pb collisions at $\sqrt{s_{_{{\rm NN}}}}$ = 2.76 TeV with the ALICE detector. The results are compared to measurements at RHIC and hydrodynamic model calculations. The mass splitting and the scaling with the number of constituent quarks of the anisotropic flow are also discussed.
119300824
Higher harmonic anisotropic flow measurements of charged particles at 2.76 TeV with the ALICE detector
We report the measurements of elliptic flow $v_{2}$, as well as higher harmonics triangular flow $v_{3}$ and quadrangular flow $v_{4}$, in $\sqrt{s_{_{NN}}} =$ 2.76 TeV Pb--Pb collisions, measured with the ALICE detector. We show that the measured elliptic and triangular flow can be understood from the initial spatial anisotropy and its event--by--event fluctuations. The resulting fluctuations of $v_{2}$ and $v_{3}$ are also discussed.
118334948
Non-Hermitian perturbations to the Fritzsch textures of lepton and quark mass matrices
Abstract We show that non-Hermitian and nearest-neighbor-interacting perturbations to the Fritzsch textures of lepton and quark mass matrices can make both of them fit current experimental data very well. In particular, we obtain θ 23 ≃ 45 ° for the atmospheric neutrino mixing angle and predict θ 13 ≃ 3 ° to 6° for the smallest neutrino mixing angle when the perturbations in the lepton sector are at the 20% level. The same level of perturbations is required in the quark sector, where the Jarlskog invariant of CP violation is about 3.7 × 10 − 5 . In comparison, the strength of leptonic CP violation is possible to reach about 1.5 × 10 − 2 in neutrino oscillations.
117546416
Majorana phases in neutrino-antineutrino oscillations
If the massive neutrinos are Majorana particles, neutrinoless double beta ($0\nu\beta\beta$) decay experiments are not enough to determine the Majorana phases. We carry out a systematic study of CP violation in neutrino-antineutrino oscillations. In these processes, CP-conserving parts involve six independent $0\nu\beta\beta$-like mass terms $\langle m\rangle_{\alpha\beta}$ and CP-violating parts are associated with nine independent Jarlskog-like parameters ${\cal V}^{ij}_{\alpha\beta}$ (for $\alpha, \beta = e, \mu, \tau$ and $i, j = 1, 2,3$). With the help of current neutrino oscillation data, we illustrate the salient features of six independent CP-violating asymmetries between $\nu_\alpha \to \bar{\nu}_\beta$ and $\bar{\nu}_\alpha \to \nu_\beta$ oscillations.
6158388
D4 brane probes in gauge/gravity duality
We propose a Dirac-Born-Infeld vertex brane+N(c) fundamental strings configuration for a probe baryon in the finite-temperature thermal gauge field via AdS/CFT correspondence. In particular, we investigate properties of this configuration in QCD(4) and warped AdS(6)xS(4). We find that, in the D4-D8 system, a holographic probe baryon can be described as N(c) fundamental strings connecting through a vertex D4 brane wrapped on S(4). In QCD(4) background, a closed vertex can exist in a confined phase but cannot exist in a deconfined phase. In the low temperature region, the screening effect still exists in the confined phase like a meson, and the vertex D4 brane dominates the baryon mass. The lower energy state corresponds to the vertex brane closer to the radial cutoff position (r=r(c)), and the higher energy state corresponds to the vertex brane a little farther away from the cutoff position. The high energy limit of this configuration is just like the unclosed vertex brane configuration in a higher temperature deconfined phase. In warped AdS(6)xS(4) background, a closed vertex can exist in a deconfined phase and the vertex contains a spike, while fundamental strings are relatively short. The screening length should be defined through the distance between the top position of the vertex spike and the boundary.