7,778 research outputs found
Sneutrino Mixing Phenomena
In any model with nonzero Majorana neutrino masses, the sneutrino and
antisneutrino of the supersymmetric extended theory mix. We outline the
conditions under which sneutrino-antisneutrino mixing is experimentally
observable. The mass-splitting of the sneutrino mass eigenstates and sneutrino
oscillation phenomena are considered.Comment: 12 pages, revtex + axodraw, 1 figure included. Minor change
Frontostriatal Maturation Predicts Cognitive Control Failure to Appetitive Cues in Adolescents
Adolescent risk-taking is a public health issue that increases the odds of poor lifetime outcomes. One factor thought to influence adolescents' propensity for risk-taking is an enhanced sensitivity to appetitive cues, relative to an immature capacity to exert sufficient cognitive control. We tested this hypothesis by characterizing interactions among ventral striatal, dorsal striatal, and prefrontal cortical regions with varying appetitive load using fMRI scanning. Child, teen, and adult participants performed a go/no-go task with appetitive (happy faces) and neutral cues (calm faces). Impulse control to neutral cues showed linear improvement with age, whereas teens showed a nonlinear reduction in impulse control to appetitive cues. This performance decrement in teens was paralleled by enhanced activity in the ventral striatum. Prefrontal cortical recruitment correlated with overall accuracy and showed a linear response with age for no-go versus go trials. Connectivity analyses identified a ventral frontostriatal circuit including the inferior frontal gyrus and dorsal striatum during no-go versus go trials. Examining recruitment developmentally showed that teens had greater between-subject ventral-dorsal striatal coactivation relative to children and adults for happy no-go versus go trials. These findings implicate exaggerated ventral striatal representation of appetitive cues in adolescents relative to an intermediary cognitive control response. Connectivity and coactivity data suggest these systems communicate at the level of the dorsal striatum differentially across development. Biased responding in this system is one possible mechanism underlying heightened risk-taking during adolescence
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Spontaneous Violation of the CP Symmetry in the Higgs Sector of the Next-to-Minimal Supersymmetric Model
The spontaneous violation of the CP symmetry in the next-to-minimal
supersymmetric standard Model (NMSSM) is investigated. It is found that the
spontaneous violation of the CP symmetry can occur in the Higgs sector of the
NMSSM for a wide region of the parameter space of the model, at the 1-loop
level where the radiative corrections due to the top quark and scalar-top quark
loops are found to generate the scalar-pseudoscalar mixings between the two
Higgs doublets of the NMSSM. In our model, we assume that the masses of the
left-handed and the right-handed scalar-top quarks are not degenerate. And we
investigate our model anaytically: We derive analytical formulae of the 1-loop
mass matrix for the neutral Higgs bosons. We calculate the upper bound on the
lightest neutral Higgs boson mass under the assumption. It is found to be about
140 GeV for our choice of parameter values in the presence of the spontaneous
violation of the CP symmetry in the NMSSM. Thus, the possibility of the
spontaneous violation of the CP symmetry is not completely ruled out in the
Higgs sector of the NMSSM if the masses of the left-handed and the right-handed
scalar-top quarks are not degenerate. Further, the phenomenology of the
- mixing within the context of our model is studied. The lower
bound on CP violating phase in the - mixing is found to increase
if either decreases or increases.Comment: 21 pages, 5 figures, To appear in Phys. Rev.
Electroweak Symmetry Breaking and BSM Physics (A Review)
In this talk, I shall first discuss the standard model Higgs mechanism and
then highlight some of its deficiencies making a case for the need to go beyond
the standard model (BSM). The BSM tour will be guided by symmetry arguments. I
shall pick up four specific BSM scenarios, namely, supersymmetry, Little Higgs,
Gauge-Higgs unification, and the Higgsless approach. The discussion will be
confined mainly on their electroweak symmetry breaking aspects.Comment: 17 pages, 10 eps figs, Based on plenary talks at the International
Conferences: WIN07, Kolkata, Jan'07, and WHEPP-10, Chennai, Jan'08. To appear
in the WHEPP-10 proceedings (a special issue of PRAMANA
Gluino Decay as a Probe of High Scale Supersymmetry Breaking
A supersymmetric standard model with heavier scalar supersymmetric particles
has many attractive features. If the scalar mass scale is O(10 - 10^4) TeV, the
standard model like Higgs boson with mass around 125 GeV, which is strongly
favored by the LHC experiment, can be realized. However, in this scenario the
scalar particles are too heavy to be produced at the LHC. In addition, if the
scalar mass is much less than O(10^4) TeV, the lifetime of the gluino is too
short to be measured. Therefore, it is hard to probe the scalar particles at a
collider. However, a detailed study of the gluino decay reveals that two body
decay of the gluino carries important information on the scalar scale. In this
paper, we propose a test of this scenario by measuring the decay pattern of the
gluino at the LHC.Comment: 29 pages, 9 figures; version published in JHE
Present status and future prospects for a Higgs boson discovery at the Tevatron and LHC
Discovering the Higgs boson is one of the primary goals of both the Tevatron
and the Large Hadron Collider (LHC). The present status of the Higgs search is
reviewed and future prospects for discovery at the Tevatron and LHC are
considered. This talk focuses primarily on the Higgs boson of the Standard
Model and its minimal supersymmetric extension. Theoretical expectations for
the Higgs boson and its phenomenological consequences are reviewed.Comment: 13 pages, 9 figures, 2 tables, jpconf documentclass file, invited
talk at PASCOS 2010, the 16th International Symposium on Particles, Strings
and Cosmology, Valencia, Spain, 19--23 July 201
Gauge Symmetry Breaking through Soft Masses in Supersymmetric Gauge Theories
Effects of soft breaking in N=1 supersymmetric gauge theories are studied.
For N_f < N_c, we include the dynamics of the non-perturbative superpotential
and use the original (s)quark and gauge fields. For N_f > N_c +1, we formulate
the dynamics in terms of dual (s)quarks and a dual gauge group SU(N_f-N_c). The
mass squared of the squarks can be negative triggering spontaneous breakdown of
flavor and color symmetry. The general condition for stability of the vacuum is
derived. We determine the breaking pattern, determine the spectrum and argue
that the masses vary smoothly as one crosses from the Higgs phase into the
confining phase, thus exhibiting complementarity.Comment: Contribution to Inauguration Conferference of Asia Pacific Center for
Theoretical Physics, 4-10 June, 1996, Seoul National University; LaTeX, no
macros neede
Radiative Neutralino Decay in Split Supersymmetry
Radiative neutralino decay is studied in a Split
Supersymmetric scenario, and compared with mSUGRA and MSSM. This 1-loop process
has a transition amplitude which is often quite small, but has the advantage of
providing a very clear and distinct signature: electromagnetic radiation plus
missing energy. In Split Supersymmetry this radiative decay is in direct
competition with the tree-level three-body decay , and we obtain large values for the branching ratio which can be close to unity in the region .
Furthermore, the value for the radiative neutralino decay branching ratio has a
strong dependence on the split supersymmetric scale , which is
otherwise very difficult to infer from experimental observables.Comment: 15 pages and 10 figure
Charged Current Universality in the MSSM
We compute the complete one-loop contributions to low-energy charged current
weak interaction observables in the Minimal Supersymmetric Standard Model
(MSSM). We obtain the constraints on the MSSM parameter space which arise when
precision low-energy charged current data are analyzed in tandem with
measurements of the muon anomaly. While the data allow the presence of at least
one light neutralino, they also imply a pattern of mass splittings among first
and second generation sleptons and squarks which contradict predictions of
widely used models for supersymmetry breaking mediation.Comment: 4 pages, 2 figure
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