702 research outputs found
Generation of defects and disorder from deeply quenching a liquid to form a solid
We show how deeply quenching a liquid to temperatures where it is linearly
unstable and the crystal is the equilibrium phase often produces crystalline
structures with defects and disorder. As the solid phase advances into the
liquid phase, the modulations in the density distribution created behind the
advancing solidification front do not necessarily have a wavelength that is the
same as the equilibrium crystal lattice spacing. This is because in a deep
enough quench the front propagation is governed by linear processes, but the
crystal lattice spacing is determined by nonlinear terms. The wavelength
mismatch can result in significant disorder behind the front that may or may
not persist in the latter stage dynamics. We support these observations by
presenting results from dynamical density functional theory calculations for
simple one- and two-component two-dimensional systems of soft core particles.Comment: 25 pages, 11 figure
Probing Yukawa Unification with K and B Mixing
We consider corrections to the unification of down-quark and charged-lepton
Yukawa couplings in supersymmetric GUTs, which links the large nu_tau-nu_mu
mixing angle to b -> s transitions. These corrections generically occur in
simple grand-unified models with small Higgs representations and affect s -> d
and b -> d transitions via the mixing of the corresponding right-handed
superpartners. On the basis of a specific SUSY-SO(10) model, we analyze the
constraints from K-Kbar and B-Bbar mixing on the additional
\tilde{d}_R-\tilde{s}_R rotation angle theta. We find that epsilon_K already
sets a stringent bound on theta, theta^{max}=O(1 degree), indicating a very
specific flavor structure of the correction operators. The impact of the large
neutrino mixings on the unitarity triangle analysis is also briefly discussed,
as well as their ability to account for the sizeable CP-violating phase
observed recently in B_s -> psi phi decays.Comment: 19 pages. Discussion in Sec. 5.2 slightly extended; minor numerical
modifications in Secs. 5.1 to 5.4, conclusions unchanged. Version to appear
in JHE
Particle-Antiparticle Mixing, epsilon_K, Delta Gamma_q, A_SL^q, A_CP(B_d -> psi K_S), A_CP(B_s -> psi phi) and B -> X_{s,d} gamma in the Littlest Higgs Model with T-Parity
We calculate a number of observables related to particle-antiparticle mixing
in the Littlest Higgs model with T-parity (LHT). The resulting effective
Hamiltonian for Delta F=2 transitions agrees with the one of Hubisz et al., but
our phenomenological analysis goes far beyond the one of these authors. In
particular, we point out that the presence of mirror fermions with new flavour
and CP-violating interactions allows to remove the possible Standard Model (SM)
discrepancy between the CP asymmetry S_{psi K_S} and large values of |V_ub| and
to obtain for the mass difference Delta M_s < (Delta M_s)_SM as suggested by
the recent result by the CDF collaboration. We also identify a scenario in
which simultaneously significant enhancements of the CP asymmetries S_{phi psi}
and A_SL^q relative to the SM are possible, while satisfying all existing
constraints, in particular from the B -> X_s gamma decay and A_CP(B -> X_s
gamma) that are presented in the LHT model here for the first time. In another
scenario the second, non-SM, value for the angle gamma=-(109+-6) from tree
level decays, although unlikely, can be made consistent with all existing data
with the help of mirror fermions. We present a number of correlations between
the observables in question and study the implications of our results for the
mass spectrum and the weak mixing matrix of mirror fermions. In the most
interesting scenarios, the latter one turns out to have a hierarchical
structure that differs significantly from the CKM one.Comment: 51 pages, 20 figures, 1 table. Extended discussion of the phases in
the new mixing matrix V_Hd, some references added or updated, conclusions
unchanged. Final version published in JHE
Universal asymptotic behavior in flow equations of dissipative systems
Based on two dissipative models, universal asymptotic behavior of flow
equations for Hamiltonians is found and discussed. Universal asymptotic
behavior only depends on fundamental bath properties but not on initial system
parameters, and the integro-differential equations possess an universal
attractor. The asymptotic flow of the Hamiltonian can be characterized by a
non-local differential equation which only depends on one parameter -
independent of the dissipative system or truncation scheme. Since the fixed
point Hamiltonian is trivial, the physical information is completely
transferred to the transformation of the observables. This yields a more stable
flow which is crucial for the numerical evaluation of correlation functions.
Furthermore, the low energy behavior of correlation functions is determined
analytically. The presented procedure can also be applied if relevant
perturbations are present as is demonstrated by evaluating dynamical
correlation functions for sub-Ohmic environments. It can further be generalized
to other dissipative systems.Comment: 15 pages, 9 figures; to appear in Phys. Rev.
Electroweak and Flavour Structure of a Warped Extra Dimension with Custodial Protection
We present the electroweak and flavour structure of a model with a warped
extra dimension and the bulk gauge group SU(3) x SU(2)_L x SU(2)_R x P_LR x
U(1)_X. The presence of SU(2)_R implies an unbroken custodial symmetry in the
Higgs system allowing to eliminate large contributions to the T parameter,
whereas the P_LR symmetry and the enlarged fermion representations provide a
custodial symmetry for flavour diagonal and flavour changing couplings of the
SM Z boson to left-handed down-type quarks. We diagonalise analytically the
mass matrices of charged and neutral gauge bosons including the first KK modes.
We present the mass matrices for quarks including heavy KK modes and discuss
the neutral and charged currents involving light and heavy fields. We give the
corresponding complete set of Feynman rules in the unitary gauge.Comment: 74 pages, 2 figures. clarifying comments and references added,
version to be published in JHE
Flavour and Collider Interplay for SUSY at LHC7
The current 7 TeV run of the LHC experiment shall be able to probe gluino and
squark masses up to values larger than 1 TeV. Assuming that hints for SUSY are
found in the jets plus missing energy channel by the end of a 5 fb run,
we explore the flavour constraints on three models with a CMSSM-like spectrum:
the CMSSM itself, a Seesaw extension of the CMSSM, and Flavoured CMSSM. In
particular, we focus on decays that might have been measured by the time the
run is concluded, such as and . We also analyse
constraints imposed by neutral meson bounds and electric dipole moments. The
interplay between collider and flavour experiments is explored through the use
of three benchmark scenarios, finding the flavour feedback useful in order to
determine the model parameters and to test the consistency of the different
models.Comment: 44 pages, 15 figures; v3: minor corrections, added references,
updated figures. Version accepted for publicatio
Footprints of the Beyond in flavor physics: Possible role of the Top Two Higgs Doublet Model
The B-factories results provide an impressive confirmation of the Standard
Model (SM) description of flavor and CP violation. Nevertheless, as more data
were accumulated, deviations in the 2.5-3.5 sigma range have emerged pointing
to the exciting possibility of new CP-odd phase(s) and flavor violating
parameters in B-decays. Primarily this seems to be the case in the time
dependent CP asymmetries in penguin dominated modes (e.g. B -> phi (eta') Ks).
We discuss these and other deviations from the SM and, as an illustration of
possible new physics scenarios, we examine the role of the Top Two Higgs
Doublet Model. This is a simple extension of the SM obtained by adding second
Higgs doublet in which the Yukawa interactions of the two Higgs doublets are
assigned in order to naturally account for the large top-quark mass.
Of course, many other extensions of the Standard Model could also account for
these experimental deviations. Clearly if one takes these deviations seriously
then some new particles in the 300 GeV to few TeV with associated new CP-odd
phase(s) are needed.Comment: 40 pages, 17 figures (png format), uses pdflate
New strategies for New Physics search in B -> K* nu anti-nu, B -> K nu anti-nu and B -> X(s) nu anti-nu decays
The rare decay B -> K* nu anti-nu allows a transparent study of Z penguin and
other electroweak penguin effects in New Physics (NP) scenarios in the absence
of dipole operator contributions and Higgs (scalar) penguin contributions that
are often more important than Z contributions in B -> K* l+l- and B(s) -> l+l-
decays. We present a new analysis of B -> K* nu anti-nu with improved form
factors and of the decays B -> K nu anti-nu and B -> X(s) nu anti-nu in the SM
and in a number of NP scenarios like the general MSSM, general scenarios with
modified Z/Z' penguins and in a singlet scalar extension of the SM. We also
summarize the results in the Littlest Higgs model with T-parity and a
Randall-Sundrum (RS) model with custodial protection of left-handed Z-di-dj
couplings. Our SM prediction BR(B -> K* nu anti-nu)=(6.8^+1.0_-1.1) x 10^-6
turns out to be significantly lower than the ones present in the literature.
Our improved calculation BR(B -> X(s) nu anti-nu)=(2.7+-0.2) x 10^-5 in the SM
avoids the normalization to the BR(B -> X(c) e anti-nu(e)) and, with less than
10% total uncertainty, is the most accurate to date. The results for the SM and
NP scenarios can be transparently summarized in a (epsilon,eta) plane with a
non-vanishing eta signalling the presence of new right-handed down-quark
flavour violating couplings which can be ideally probed by the decays in
question. Measuring the three branching ratios and one additional polarization
observable in B -> K* nu anti-nu allows to overconstrain the resulting point in
the (epsilon,eta) plane with (epsilon,eta)=(1,0) corresponding to the SM. The
correlations of these three channels with the rare decays K+ -> pi+ nu anti-nu,
KL -> pi0 nu anti-nu, B -> X(s) l+ l- and B(s) -> mu+ mu- offer powerful tests
of New Physics with new right-handed couplings and non-MFV interactions.Comment: 31 pages, 14 figures, 3 tables. v2: 9 references, minor
clarifications and corrections added. Conclusions unchange
Charmless hadronic decays and new physics effects in the general two-Higgs doublet models
Based on the low-energy effective Hamiltonian with the generalized
factorization, we calculate the new physics contributions to the branching
ratios of the two-body charmless hadronic decays of and mesons
induced by the new gluonic and electroweak charged-Higgs penguin diagrams in
the general two-Higgs doublet models (models I, II and III). Within the
considered parameter space, we find that: (a) the new physics effects from new
gluonic penguin diagrams strongly dominate over those from the new -
and - penguin diagrams; (b) in models I and II, new physics contributions
to most studied B meson decay channels are rather small in size: from -15% to
20%; (c) in model III, however, the new physics enhancements to the
penguin-dominated decay modes can be significant, , and
therefore are measurable in forthcoming high precision B experiments; (d) the
new physics enhancements to ratios {\cal B}(B \to K \etap) are significant in
model III, , and hence provide a simple and plausible new
physics interpretation for the observed unexpectedly large B \to K \etap
decay rates; (e) the theoretical predictions for and
in model III are still consistent with the data
within errors; (f) the significant new physics enhancements to the
branching ratios of and decays are helpful to improve the
agreement between the data and the theoretical predictions; (g) the theoretical
predictions of in the 2HDM's are generally
consistent with experimental measurements and upper limits ()Comment: 55 pages, Latex file, 17 PS and EPS figures. With minor corrections,
final version to be published in Phys.Rev. D. Repot-no: PKU-TH-2000-4
Charm multiplicity and the branching ratios of inclusive charmless b quark decays in the general two-Higgs-doublet models
In the framework of general two-Higgs-doublet models, we calculate the
branching ratios of various inclusive charmless b decays by using the low
energy effective Hamiltonian including next-to-leading order QCD corrections,
and examine the current status and the new physics effects on the determination
of the charm multiplicity and semileptonic branching ratio .
Within the considered parameter space, the enhancement to the ratio due to the charged-Higgs penguins can be as large as a factor of 8 (3) in
the model III (II), while the ratio can be increased from
the standard model prediction of 2.49% to 4.91% (2.99%) in the model III (II).
Consequently, the value of and can be decreased simultaneously
in the model III. The central value of will be lowered slightly by
about 0.003, but the ratio can be reduced significantly from the
theoretical prediction of in the SM to , for GeV, respectively. We find that
the predicted and the measured now agree within roughly one
standard deviation after taking into account the effects of gluonic charged
Higgs penguins in the model III with a relatively light charged Higgs boson.Comment: 25 pages, Latex file, axodraw.sty, 6 figures. Final version to be
published in Phys.Rev.
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