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Physics prospects of the KTeV experiment at Fermilab
KTeV is a new Fermilab fixed target experiment which will search for direct CP violation in the neutral kaon system. In addition, we will make precision measurements of other CP and CPT violating parameters and make high sensitivity studies of rare kaon decays. The detector has been commissioned and is currently taking data. The physics goals and detector performance are presented. 12 refs., 1 fig
Flavor Changing Effects in Family Nonuniversal Z' Models
Flavor-changing and CP-violating interactions of Z' to fermions are generally
present in models with extra U(1) gauge symmetry that are string-inspired or
related to broken gauged family symmetry. We study the consequences of such
couplings in fermion electric dipole moments, muon g-2, and K and B meson
mixings. From experimental limits or measured values, we constrain the
off-diagonal Z' couplings to fermions. Some of these constraints are comparable
or stronger than the existing constraints obtained from other observables.Comment: 17 pages, 2 figure
V(us) Determination from Hyperon Semileptonic Decays
We analyze the numerical determination of the quark mixing factor V(us) from
hyperon semileptonic decays. The discrepancies between the results obtained in
two previous studies are clarified. Our fits indicate sizeable SU(3) breaking
corrections, which unfortunately can only be fully determined from the data at
the first order. The lack of a reliable theoretical calculation of second-order
symmetry breaking effects translates into a large systematic uncertainty, which
has not been taken into account previously. Our final result, V(us) = 0.226 +/-
0.005, is not competitive with the existing determinations from K(l3), K(l2)
and \tau decays.Comment: 16 pages, no figures. References added and other minor change
epsilon'/epsilon at the NLO: 10 Years Later
During the last four years several parameters relevant for the analysis of
the CP-violating ratio epsilon'/epsilon improved and/or changed significantly.
In particular, the experimental value of epsilon'/epsilon and the strange quark
mass decreased, the uncertainty in the CKM factor has been reduced, and for a
value of the hadronic matrix element of the dominant electroweak penguin
operator Q_8, some consensus has been reached among several theory groups. In
view of this situation, ten years after the first analyses of epsilon'/epsilon
at the next-to-leading order, we reconsider the analysis of epsilon'/epsilon
within the SM and investigate what can be said about the hadronic Q_6 matrix
element of the dominant QCD penguin operator on the basis of the present
experimental value of epsilon'/epsilon and todays values of all other
parameters.
Employing a conservative range for the reduced electroweak penguin matrix
element R_8=1.0+-0.2 from lattice QCD, and present values for all other input
parameters, on the basis of the current world average for epsilon'/epsilon, we
obtain the reduced hadronic matrix element of the dominant QCD penguin operator
R_6=1.23+-0.16 implying _0^NDR(m_c) ~ -0.8 _2^NDR(m_c). We compare
these results with those obtained in large-N_c approaches in which generally
R_6 ~ R_8 and _0^NDR(m_c) is chirally suppressed relatively to
_2^NDR(m_c). We present the correlation between R_6 and R_8 that is
implied by the data on epsilon'/epsilon provided new physics contributions to
epsilon'/epsilon can be neglected.Comment: 18 pages, 1 eps figure, version to appear in JHE
KL to pi0 e+ e- and KL to pi0 mu+ mu- : A binary star on the stage of flavor physics
A systematic analysis of New Physics impacts on the rare decays KL to pi0 l+
l- is performed. Thanks to their different sensitivities to flavor-changing
local effective interactions, these two modes could provide valuable
information on the nature of the possible New Physics at play. In particular, a
combined measurement of both modes could disentangle scalar/pseudoscalar from
vector or axial-vector contributions. For the latter, model-independent bounds
are derived. Finally, the KL to pi0 mu+ mu- forward-backward CP-asymmetry is
considered, and shown to give interesting complementary information.Comment: 20 pages, 5 figures. Comments and references added, minor numerical
changes, conclusion unchanged, to appear in JHE
The <SPP> Green function and SU(3) breaking in Kl3 decays
Using the 1=/N-C expansion scheme and truncating the hadronic spectrum to the lowest-lying resonances, we match a meromorphic approximation to the Green function onto QCD by imposing the correct large-momentum falloff, both off- shell and on the relevant hadron mass shells. In this way we determine a number of chiral low-energy constants of O(p(6)), in particular the ones governing SU(3) breaking in the K-l3 vector form factor at zero momentum transfer. The main result of our matching procedure is that the known loop contributions largely dominate the corrections of O(p(6)) to f(+)(0). We discuss the implications of our final value f(+)(K0 pi-) (0) = 0.984 +/- 0.012 for the extraction of V-us from K-l3 decays
Tests of the fundamental symmetries in eta meson decays
Patterns of chiral symmetry violation and tests of the conservation of the
fundamental C, P and CP symmetries are key physics issues in studies of the
pi0, eta and eta' meson decays. These tests include searches for rare or
forbidden decays and searches for asymmetries among the decay products in the
not-so-rare decays. Some examples for the rare decays are eta-->2pi, eta-->4pi0
(CP tests), decays into an odd number of photons (e.g., eta-->3g) and the decay
eta-->pi0e+e- (C tests). The experimental studies of the pi0, eta and eta'
meson decays are carried out at four European accelerator research facilities:
KLOE/KLOE-2 at DAFNE (Frascati), Crystal Ball at MAMI (Mainz), WASA at COSY
(J\"ulich), Crystal Barrel at ELSA (Bonn).Comment: 9 pages, 2 figures, proceedings of Symposium on Prospects in the
Physics of Discrete Symmetries, DISCRETE 2010, 6 - 11 December, Rome; v2:
added reference
Search for the Rare Decay K_{L}\to\pi^{0}\pi^{0}\gamma
The KTeV E799 experiment has conducted a search for the rare decay
via the topology
(where ). Due to Bose
statistics of the pair and the real nature of the photon, the
decay is restricted to proceed at lowest order
by the CP conserving direct emission (DE) of an E2 electric quadrupole photon.
The rate of this decay is interesting theoretically since chiral perturbation
theory predicts that this process vanishes at level . Therefore, this
mode probes chiral perturbation theory at . In this paper we report a
determination of an upper limit of (90% CL) for
. This is approximately a factor of 20 lower than
previous results.Comment: six pages and six figures in the submission. Reformatted for Physics
Review
Search for the Rare Decays KL->pi0pi0mu+mu- and KL->pi0pi0X0->pi0pi0mu+mu-
The KTeV E799 experiment has conducted a search for the rare decays
KL->pi0pi0mu+mu- and KL->pi0pi0X0->pi0pi0mu+mu-, where the X0 is a possible new
neutral boson that was reported by the HyperCP experiment with a mass of (214.3
pm 0.5) MeV/c^{2}. We find no evidence for either decay. We obtain upper limits
of Br(KL->pi0pi0X0->pi0pi0mu+mu-) pi0pi0mu+mu-) <
9.2 x 10^{-11} at the 90% confidence level. This result rules out the
pseudoscalar X0 as an explanation of the HyperCP result under the scenario that
the \bar{d}sX0 coupling is completely real