482 research outputs found
The Impact of a 4th Generation on Mixing and CP Violation in the Charm System
We study D0-D0 mixing in the presence of a fourth generation of quarks. In
particular, we calculate the size of the allowed CP violation which is found at
the observable level well beyond anything possible with CKM dynamics. We
calculate the semileptonic asymmetry a_SL and the mixing induced CP asymmetry
eta_fS_f which are correlated with each other. We also investigate the
correlation of eta_fS_f with a number of prominent observables in other mesonic
systems like epsilon'/epsilon, Br(K_L -> pi0 nu nu), Br(K+ -> pi+ nu nu),
Br(B_s ->mu+ mu-), Br(B_d -> mu+ mu-) and finally S_psi phi in the B_s system.
We identify a clear pattern of flavour and CP violation predicted by the SM4
model: While simultaneous large 4G effects in the K and D systems are possible,
accompanying large NP effects in the B_d system are disfavoured. However this
behaviour is not as pronounced as found for the LHT and RSc models. In contrast
to this, sizeable CP violating effects in the B_s system are possible unless
extreme effects in eta_fS_f are found, and Br(B_s ->mu+ mu-) can be strongly
enhanced regardless of the situation in the D system. We find that, on the
other hand, S_psi phi > 0.2 combined with the measured epsilon'/epsilon
significantly diminishes 4G effects within the D system.Comment: 22 pages, 23 figures, v2 (references added
Waiting for Precise Measurements of K^+->pi^+ nu nu and K_L->pi^0 nu nu
In view of future plans for accurate measurements of the theoretically clean
branching ratios Br(K+ -> pi+ nu nu) and Br(KL -> pi0 nu nu), that should take
place in the next decade, we collect the relevant formulae for quantities of
interest and analyze their theoretical and parametric uncertainties. We point
out that in addition to the angle beta in the unitarity triangle (UT) also the
angle gamma can in principle be determined from these decays with respectable
precision and emphasize in this context the importance of the recent NNLO QCD
calculation of the charm contribution to K+ -> pi+ nu nu and of the improved
estimate of the long distance contribution by means of chiral perturbation
theory. In addition to known expressions we present several new ones that
should allow transparent tests of the Standard Model (SM) and of its
extensions. While our presentation is centered around the SM, we also discuss
models with minimal flavour violation and scenarios with new complex phases in
decay amplitudes and meson mixing. We give a brief review of existing results
within specific extensions of the SM, in particular the Littlest Higgs Model
with T-parity, Z' models, the MSSM and a model with one universal extra
dimension. We derive a new "golden" relation between B and K systems that
involves (beta,gamma) and Br(KL -> pi0 nu nu) and investigate the virtues of
(R_t,beta), (R_b,gamma), (beta,gamma) and (etabar,gamma) strategies for the UT
in the context of K -> pi nu nu decays with the goal of testing the SM and its
extensions.Comment: 56 pages, 18 figures, Section on Long Distance Contributions, 2
Figures and few References added, Uses Rev Mod Phys Style; Includes new
results of NNLO calculation as well as matrix elements, extended and modified
sections on new physic
The production of the new gauge boson via collision in the littlest Higgs model
The new lightest gauge boson with mass of a few hundred GeV is
predicted in the littlest Higgs model. should be accessible in the planed
ILC and the observation of such particle can strongly support the littlest
Higgs model. The realization of and collision will
open a wider window to probe . In this paper, we study the new gauge boson
production processes and
at the ILC. Our results show that the production
cross section of the process is less than one fb
in the most parameter spaces while the production cross section of the process
can reach the level of tens fb and even
hundreds of fb in the sizable parameter spaces allowed by the electroweak
precision data. With the high luminosity, the sufficient typical signals could
be produced, specially via . Because the
final electron and photon beams can be easily identified and the signal can be
easily distinguished from the background produced by and decaying,
should be detectable via collision at the ILC. Therefore, the
processes and
provide a useful way to detect and test the littlest Higgs model.Comment: 15 pages, 3 figures. Some typos have been corrected, we have added
some new references, and there are also some changes in equation 1
Effect of FCNC mediated Z boson on lepton flavor violating decays
We study the three body lepton flavor violating (LFV) decays , and the semileptonic decay in the flavor changing neutral current (FCNC) mediated boson
model. We also calculate the branching ratios for LFV leptonic B decays,
, , and the
conversion of muon to electron in Ti nucleus. The new physics parameter space
is constrained by using the experimental limits on and
. We find that the branching ratios for and processes could be as large as and . For other LFV B decays the branching ratios are found to be too
small to be observed in the near future.Comment: 15 pages, 8 figures, typos corrected, one more section added, version
to appear in EPJ
LHC Predictions from a Tevatron Anomaly in the Top Quark Forward-Backward Asymmetry
We examine the implications of the recent CDF measurement of the top-quark
forward-backward asymmetry, focusing on a scenario with a new color octet
vector boson at 1-3 TeV. We study several models, as well as a general
effective field theory, and determine the parameter space which provides the
best simultaneous fit to the CDF asymmetry, the Tevatron top pair production
cross section, and the exclusion regions from LHC dijet resonance and contact
interaction searches. Flavor constraints on these models are more subtle and
less severe than the literature indicates. We find a large region of allowed
parameter space at high axigluon mass and a smaller region at low mass; we
match the latter to an SU(3)xSU(3)/SU(3) coset model with a heavy vector-like
fermion. Our scenario produces discoverable effects at the LHC with only 1-2
inverse femtobarns of luminosity at 7-8 TeV. Lastly, we point out that a
Tevatron measurement of the b-quark forward-backward asymmetry would be very
helpful in characterizing the physics underlying the top-quark asymmetry.Comment: 35 pages, 10 figures, 4 table
Effects of T- and P-odd weak nucleon interaction in nuclei: renormalizations due to residual strong interaction, matrix elements between compound states and their correlations with P-violating matrix elements
Manifestations of P-,T-odd weak interaction between nucleons in nucleus are
considered. Renormalization of this interaction due to residual strong
interaction is studied. Mean squared matrix elements of P-,T-odd weak
interaction between compound states are calculated. Correlators between
P-,T-odd and P-odd, T-even weak interaction matrix elements between compound
states are considered and estimates for these quantities are obtained.Comment: Submitted to Phys. Rev. C; 21 pages, REVTEX 3, no figure
Event-related alpha suppression in response to facial motion
This article has been made available through the Brunel Open Access Publishing Fund.While biological motion refers to both face and body movements, little is known about the visual perception of facial motion. We therefore examined alpha wave suppression as a reduction in power is thought to reflect visual activity, in addition to attentional reorienting and memory processes. Nineteen neurologically healthy adults were tested on their ability to discriminate between successive facial motion captures. These animations exhibited both rigid and non-rigid facial motion, as well as speech expressions. The structural and surface appearance of these facial animations did not differ, thus participants decisions were based solely on differences in facial movements. Upright, orientation-inverted and luminance-inverted facial stimuli were compared. At occipital and parieto-occipital regions, upright facial motion evoked a transient increase in alpha which was then followed by a significant reduction. This finding is discussed in terms of neural efficiency, gating mechanisms and neural synchronization. Moreover, there was no difference in the amount of alpha suppression evoked by each facial stimulus at occipital regions, suggesting early visual processing remains unaffected by manipulation paradigms. However, upright facial motion evoked greater suppression at parieto-occipital sites, and did so in the shortest latency. Increased activity within this region may reflect higher attentional reorienting to natural facial motion but also involvement of areas associated with the visual control of body effectors. © 2014 Girges et al
The Impact of Flavour Changing Neutral Gauge Bosons on B->X_s gamma
The branching ratio of the rare decay B->X_s gamma provides potentially
strong constraints on models beyond the Standard Model. Considering a general
scenario with new heavy neutral gauge bosons, present in particular in Z' and
gauge flavour models, we point out two new contributions to the B->X_s gamma
decay. The first one originates from one-loop diagrams mediated by gauge bosons
and heavy exotic quarks with electric charge -1/3. The second contribution
stems from the QCD mixing of neutral current-current operators generated by
heavy neutral gauge bosons and the dipole operators responsible for the B->X_s
gamma decay. The latter mixing is calculated here for the first time. We
discuss general sum rules which have to be satisfied in any model of this type.
We emphasise that the neutral gauge bosons in question could also significantly
affect other fermion radiative decays as well as non-leptonic two-body B
decays, epsilon'/epsilon, anomalous (g-2)_mu and electric dipole moments.Comment: 31 pages, 5 figures; version published on JHEP; added magic QCD
numbers for flavour-violating Z gauge boson contribution to B -> X_s gamm
First Person Experience of Body Transfer in Virtual Reality
Background: Altering the normal association between touch and its visual correlate can result in the illusory perception of a fake limb as part of our own body. Thus, when touch is seen to be applied to a rubber hand while felt synchronously on the corresponding hidden real hand, an illusion of ownership of the rubber hand usually occurs. The illusion has also been demonstrated using visuomotor correlation between the movements of the hidden real hand and the seen fake hand. This type of paradigm has been used with respect to the whole body generating out-of-the-body and body substitution illusions. However, such studies have only ever manipulated a single factor and although they used a form of virtual reality have not exploited the power of immersive virtual reality (IVR) to produce radical transformations in body ownership.Principal Findings: Here we show that a first person perspective of a life-sized virtual human female body that appears to substitute the male subjects' own bodies was sufficient to generate a body transfer illusion. This was demonstrated subjectively by questionnaire and physiologically through heart-rate deceleration in response to a threat to the virtual body. This finding is in contrast to earlier experimental studies that assume visuotactile synchrony to be the critical contributory factor in ownership illusions. Our finding was possible because IVR allowed us to use a novel experimental design for this type of problem with three independent binary factors: (i) perspective position (first or third), (ii) synchronous or asynchronous mirror reflections and (iii) synchrony or asynchrony between felt and seen touch.Conclusions: The results support the notion that bottom-up perceptual mechanisms can temporarily override top down knowledge resulting in a radical illusion of transfer of body ownership. The research also illustrates immersive virtual reality as a powerful tool in the study of body representation and experience, since it supports experimental manipulations that would otherwise be infeasible, with the technology being mature enough to represent human bodies and their motion
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