45 research outputs found
Total Acquisition in Graphs
Let G be a weighted graph in which each vertex initially has weight 1. A total acquisition move transfers all the weight from a vertex u to a neighboring vertex v, under the condition that before the move the weight on v is at least as large as the weight on u. The (total) acquisition number of G, written at(G), is the minimum size of the set of vertices with positive weight after a sequence of total acquisition moves. Among connected n-vertex graphs, at(G) is maximized by trees. The maximum is Θ(√(n lg n) for trees with diameter 4 or 5. It is⌊(n + 1)/3⌋ for trees with diameter between 6 and (2/3)(n + 1), and it is⌈(2n – 1 – D)/4⌉ for trees with diameter D when (2/3)(n + 1) ≤ D ≤ n - 1. We characterize trees with acquisition number 1, which permits testing at(G) ≤ k in time O(nk+2) on trees. If G ≠C5, then min{at(G), at()} = 1. If G has diameter 2, then at(G) ≤ 32 ln n ln ln n; we conjecture a constant upper bound. Indeed, at(G) = 1 when G has diameter 2 and no 4-cycle, except for four graphs with acquisition number 2. Deleting one edge of an n-vertex graph cannot increase at by more than 6.84√n, but we construct an n-vertex tree with an edge whose deletion increases it by more than (1/2)√n. We also obtain multiplicative upper bounds under products
Supersymmetric Baryogenesis and Flavor Physics
We study the flavor physics implications of baryogenesis in the Minimal
Supersymmetric Standard Model. Enhanced mixing and
rates are generic to all scenarios. Depending on the origin of the CP violating
phase responsible for baryogenesis there could be a large neutron electric
dipole moment, large CP violating mixing or CP violation in top
quark production. We discuss how the combination of these measurements with the
requirement of baryogenesis shed light on the MSSM parameter space and the
source of CP violation.Comment: PRL version. Suppression factor explicitly identified below Eq. 5.
More references added. Minor cosmetic changes in discussions. All results
unchange
A New Supersymmetric CP Violating Contribution to Neutral Meson Mixing
We study the contribution to flavor changing neutral current processes from
box diagrams with light higgsinos and squarks. Starting with just the Cabbibo
Kobayashi Maskawa (CKM) phase, we find contributions to the and
meson mass matrices that are out of phase with the Standard Model contributions
in the case of substantial mixing between the up-type squarks. This difference
in phase could be large enough to be detected at the proposed factories,
with interesting implications for the unitarity triangle of CKM matrix
elements.Comment: 1 reference added, 1 reference clarified, 2 typos corrected (QCD
corrections to K meson mixing in Tables 1 and 3). To be published in Phys.
Rev. D. 15 pages (Latex), 2 figures and epsfig.sty submitte
CP Asymmetry in B_d --> phi K_S: Standard Model Pollution
The difference in the time dependent CP asymmetries between the modes and is a clean signal for physics beyond the Standard
Model. This interpretation could fail if there is a large enhancement of the
matrix element of the operator between the initial state
and the final state. We argue against this possibility and propose
some experimental tests that could shed light on the situation.Comment: 9 pages, Revte
Constraining the CKM Parameters using CP Violation in semi-leptonic B Decays
We discuss the usefulness of the CP violating semi-leptonic asymmetry a_{SL}
not only as a signal of new physics, but also as a tool in constraining the CKM
parameters. We show that this technique could yield useful results in the first
years of running at the B factories. We present the analysis graphically in
terms of M_{12}, the dispersive part of the B-Bbar mixing amplitude. This is
complementary to the usual unitarity triangle representation and often allows a
cleaner interpretation of the data.Comment: 15 pages REVTEX, 7 figure
Oblique Corrections To The W Width
The lowest-order expression for the partial width to , has no oblique radiative
corrections from new physics if the measured mass is used. Here GeV/ is the muon decay constant. For
the present value of GeV/, and with
GeV, one expects MeV. The total
width is also expected to lack oblique corrections from
new physics, so that . Present data are consistent with this prediction.Comment: 15 pages (LaTeX), one PostScript figure not included (available upon
request
Supersymmetric Baryogenesis at the Electroweak Phase Transition
We study the possibility of baryogenesis in the case of supersymmetry
breaking with large mixing between the right-handed scalar charm and
right-handed scalar top or right-handed scalar up and right-handed scalar top
squarks resulting in one light right-handed up-type squark mass eigenstate. We
argue that in this case the electroweak phase transition will be first order,
and that large phases already present in the quark mass matrices can generate a
baryon asymmetry of the correct magnitude without introducing any new phases
specifically for this purpose. We study in detail a particular ansatz for
supersymmetry breaking and CP violation where there is only one CP violating
phase in the theory: in the up-type quark mass matrix. We study the constraints
placed on this model by baryogenesis and flavor physics. This scenario has
robust implications for low energy flavor phsyics including D-Dbar mixing and
an electric dipole moment for the neutron that are close to the experimental
bounds, and CP violation in the B-Bbar system that is different from that in
the Standard Model.Comment: Final PRD version. 2 typos (Eqs. 24 and 47) correcte
SUSY GUTs contributions and model independent extractions of CP phases
We consider the origin of new phases in supersymmetric grand unification
model, and show how significant new contributions arise from the gluino
mediated diagram. We then present a more general model independent analysis of
various modes of B-decays suggested previously for measurement of the CKM
phases and point out what they really measure. It is in principle possible to
separate out all the phases.Comment: 13 pages (Latex), 2 PS figures, a few remarks are added and a typo is
corrected. To appear in Phys. Rev. Let
Signatures of Baryogenesis in the MSSM
We revisit the electroweak baryogenesis within the context of the minimal
supersymmetric standard model (MSSM), studying its potential collider
signatures. We find that this mechanism of baryogenesis does not give a new CP
violating signal at the -factories. The first circumstantial evidence may
come from enhanced or mixing. If a light right-handed scalar top
and Higgs are found as required, a linear collider represents the best
possibility for confirming the scenario.Comment: 5 pages, 2 figures. Minor typos fixed. Reference Adde
CP violation in chargino decays in the MSSM
In the minimal supersymmetric standard model (MSSM) with complex parameters,
supersymmetric loop effects can lead to \emph{CP} violation. We calculate the
rate asymmetries of decays of charginos into the lightest neutralino and a
boson on the basis of the most important loop contributions in the third
generation squark sectors. It turns out that the \emph{CP} violating
asymmetries can be a few per cent in typical regions of the parameter space of
the MSSM. These processes would provide very promising channels for probing
\emph{CP} violation in the MSSM at future high-energy colliders.Comment: 15 pages, 5 figures, LaTeX2