280 research outputs found
Reparametrization Invariance of Path Integrals
We demonstrate the reparametrization invariance of perturbatively defined
one-dimensional functional integrals up to the three-loop level for a path
integral of a quantum-mechanical point particle in a box. We exhibit the origin
of the failure of earlier authors to establish reparametrization invariance
which led them to introduce, superfluously, a compensating potential depending
on the connection of the coordinate system. We show that problems with
invariance are absent by defining path integrals as the epsilon-> 0 -limit of
1+ epsilon -dimensional functional integrals.Comment: Author Information under
http://www.physik.fu-berlin.de/~kleinert/institution.html . Latest update of
paper also at
http://www.physik.fu-berlin.de/~kleinert/kleiner_re289/preprint.htm
Spectrum of k-string tensions in SU(N) gauge theories
We compute, for the four-dimensional SU(4) and SU(6) gauge theories
formulated on a lattice, the string tensions sigma_k related to sources with
Z_N charge k, using Monte Carlo simulations. Our results are compatible with
sigma_k \propto sin (k pi/N), and show sizeable deviations from Casimir
scaling.Comment: Lattice2001(confinement
Folded Supersymmetry and the LEP Paradox
We present a new class of models that stabilize the weak scale against
radiative corrections up to scales of order 5 TeV without large corrections to
precision electroweak observables. In these `folded supersymmetric' theories
the one loop quadratic divergences of the Standard Model Higgs field are
cancelled by opposite spin partners, but the gauge quantum numbers of these new
particles are in general different from those of the conventional
superpartners. This class of models is built around the correspondence that
exists in the large N limit between the correlation functions of supersymmetric
theories and those of their non-supersymmetric orbifold daughters. By
identifying the mechanism which underlies the cancellation of one loop
quadratic divergences in these theories, we are able to construct simple
extensions of the Standard Model which are radiatively stable at one loop.
Ultraviolet completions of these theories can be obtained by imposing suitable
boundary conditions on an appropriate supersymmetric higher dimensional theory
compactified down to four dimensions. We construct a specific model based on
these ideas which stabilizes the weak scale up to about 20 TeV and where the
states which cancel the top loop are scalars not charged under Standard Model
color. Its collider signatures are distinct from conventional supersymmetric
theories and include characteristic events with hard leptons and missing
energy.Comment: 18 pages, 5 figures, references correcte
Supersymmetric Quantum Chromodynamics: How Confined Non-Abelian Monopoles Emerge from Quark Condensation
We consider N =1 supersymmetric QCD with the gauge group U(N) and N_f=N quark
flavors. To get rid of flat directions we add a meson superfield. The theory
has no adjoint fields and, therefore, no 't Hooft-Polyakov monopoles in the
quasiclassical limit. We observe a non-Abelian Meissner effect: condensation of
color charges (squarks) gives rise to confined monopoles. The very fact of
their existence in N =1 supersymmetric QCD without adjoint scalars was not
known previously. Our analysis is analytic and is based on the fact that the N
=1 theory under consideration can be obtained starting from N =2 SQCD in which
the 't Hooft-Polyakov monopoles do exist, through a certain limiting procedure
allowing us to track the status of these monopoles at various stages. Monopoles
are confined by BPS non-Abelian strings (flux tubes). Dynamics of string
orientational zero modes are described by supersymmetric CP(N-1) sigma model on
the string world sheet. If a dual of N =1 SQCD with the gauge group U(N) and
N_f=N quark flavors could be identified, in this dual theory our demonstration
would be equivalent to the proof of the non-Abelian dual Meissner effect.Comment: 33 pages, 3 figures. V2 reference and a brief comment added; typos
corrected. V3 two comments added; final version accepted for publication to
PR
Duality cascades and duality walls
We recast the phenomenon of duality cascades in terms of the Cartan matrix
associated to the quiver gauge theories appearing in the cascade. In this
language, Seiberg dualities for the different gauge factors correspond to Weyl
reflections. We argue that the UV behavior of different duality cascades
depends markedly on whether the Cartan matrix is affine ADE or not. In
particular, we find examples of duality cascades that can't be continued after
a finite energy scale, reaching a "duality wall", in terminology due to M.
Strassler. For these duality cascades, we suggest the existence of a UV
completion in terms of a little string theory.Comment: harvmac, 24 pages, 4 figures. v2: references added. v3: reference
adde
Anarchy and Hierarchy
We advocate a new approach to study models of fermion masses and mixings,
namely anarchy proposed in hep-ph/9911341. In this approach, we scan the O(1)
coefficients randomly. We argue that this is the correct approach when the
fundamental theory is sufficiently complicated. Assuming there is no physical
distinction among three generations of neutrinos, the probability distributions
in MNS mixing angles can be predicted independent of the choice of the measure.
This is because the mixing angles are distributed according to the Haar measure
of the Lie groups whose elements diagonalize the mass matrices. The
near-maximal mixings, as observed in the atmospheric neutrino data and as
required in the LMA solution to the solar neutrino problem, are highly
probable. A small hierarchy between the Delta m^2 for the atmospheric and the
solar neutrinos is obtained very easily; the complex seesaw case gives a
hierarchy of a factor of 20 as the most probable one, even though this
conclusion is more measure-dependent. U_{e3} has to be just below the current
limit from the CHOOZ experiment. The CP-violating parameter sin delta is
preferred to be maximal. We present a simple SU(5)-like extension of anarchy to
the charged-lepton and quark sectors which works well phenomenologically.Comment: 26 page
The LHC Phenomenology of Vectorlike Confinement
We investigate in detail the LHC phenomenology of "vectorlike confinement",
where the Standard Model is augmented by a new confining gauge interaction and
new light fermions that carry vectorlike charges under both the Standard Model
and the new gauge group. If the new interaction confines at the TeV scale, this
framework gives rise to a wide range of exotic collider signatures such as the
production of a vector resonance that decays to a pair of collider-stable
charged massive particles (a "di-CHAMP" resonance), to a pair of
collider-stable massive colored particles (a "di-R-hadron resonance), to
multiple photons, s and s via two intermediate scalars, and/or to
multi-jet final states. To study these signals at the LHC, we set up two
benchmark models: one for the di-CHAMP and multi-photon signals, and the other
for the di-R-hadron and multijet signals. For the di-CHAMP/multi-photon model,
Standard Model backgrounds are negligible, and we show that a full
reconstruction of the spectrum is possible, providing powerful evidence for
vectorlike confinement. For the di-R-hadron/multijet model, we point out that
in addition to the di-R-hadron signal, the rate of the production of four
R-hadrons can also be sizable at the LHC. This, together with the multi-jet
signals studied in earlier work, makes it possible to single out vectorlike
confinement as the underlying dynamics.Comment: 32 pages, 28 figures. Several typos fixed, one paragraph added
elaborating choice of benchmarks. Version accepted by JHEP
Long-Lived Neutralino NLSPs
We investigate the collider signatures of heavy, long-lived, neutral
particles that decay to charged particles plus missing energy. Specifically, we
focus on the case of a neutralino NLSP decaying to Z and gravitino within the
context of General Gauge Mediation. We show that a combination of searches
using the inner detector and the muon spectrometer yields a wide range of
potential early LHC discoveries for NLSP lifetimes ranging from 10^(-1)-10^5
mm. We further show that events from Z(l+l-) can be used for detailed kinematic
reconstruction, leading to accurate determinations of the neutralino mass and
lifetime. In particular, we examine the prospects for detailed event study at
ATLAS using the ECAL (making use of its timing and pointing capabilities)
together with the TRT, or using the muon spectrometer alone. Finally, we also
demonstrate that there is a region in parameter space where the Tevatron could
potentially discover new physics in the delayed Z(l+l-)+MET channel. While our
discussion centers on gauge mediation, many of the results apply to any
scenario with a long-lived neutral particle decaying to charged particles.Comment: 31 pages, 12 figure
Induced N=2 composite supersymmetry in 2+1 dimensions
Starting from N=1 scalar supermultiplets in 2+1 dimensions, we build
explicitly the composite superpartners which define a N=2 superalgebra induced
by the initial N=1 supersymmetry. The occurrence of this extension is linked to
the topologically conserved current out of which the composite superpartners
are constructed.Comment: 11 pages LATEX, no figure
A Composite Little Higgs Model
We describe a natural UV complete theory with a composite little Higgs. Below
a TeV we have the minimal Standard Model with a light Higgs, and an extra
neutral scalar. At the TeV scale there are additional scalars, gauge bosons,
and vector-like charge 2/3 quarks, whose couplings to the Higgs greatly reduce
the UV sensitivity of the Higgs potential. Stabilization of the Higgs mass
squared parameter, without finetuning, occurs due to a softly broken shift
symmetry--the Higgs is a pseudo Nambu-Goldstone boson. Above the 10 TeV scale
the theory has new strongly coupled interactions. A perturbatively
renormalizable UV completion, with softly broken supersymmetry at 10 TeV is
explicitly worked out. Our theory contains new particles which are odd under an
exact "dark matter parity", (-1)^{(2S+3B+L)}. We argue that such a parity is
likely to be a feature of many theories of new TeV scale physics. The lightest
parity odd particle, or "LPOP", is most likely a neutral fermion, and may make
a good dark matter candidate, with similar experimental signatures to the
neutralino of the MSSM. We give a general effective field theory analysis of
the calculation of corrections to precision electroweak observables.Comment: 28 page
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