378 research outputs found
Z+jet production at the LHC: Electroweak radiative corrections
The investigation of weak bosons (, )
produced with or without associated hard QCD jets will be of great
phenomenological interest at the LHC. Owing to the large cross sections and the
clean decay signatures of the vector bosons, weak-boson production can be used
to monitor and calibrate the luminosity of the collider, to constrain the PDFs,
or to calibrate the detector. Moreover, the +jet(s) final state constitutes
an important background to a large variety of signatures of physics beyond the
Standard Model. To match the excellent experimental accuracy that is expected
at the LHC, we have worked out a theoretical next-to-leading-order analysis of
+jet production at hadron colliders. The focus of this talk will be on new
results on the full electroweak corrections to +jet production
at the LHC. All off-shell effects are included in our approach, and the finite
lifetime of the boson is consistently accounted for using the complex-mass
scheme. In the following, we briefly introduce the calculation and discuss
selected phenomenological implications of our results.Comment: 5 pages, 2 figures, talk at the "35th International Conference on
High Energy Physics", Paris, France, July 22 -- 28, 201
Non-local Higgs actions: Tree-level electroweak constraints and high-energy unitarity
We consider electroweak symmetry breaking by a certain class of non-local
Higgs sectors. Extending previous studies employing the Mandelstam condition, a
straight Wilson line is used to make the Higgs action gauge invariant. We show
the unitarization of vector-boson scattering for a wide class of non-local
actions, but find that the Wilson-line model leads to tree-level corrections to
electroweak precision observables, which restrict the parameter space of the
model. We also find that Unhiggs models cannot address the hierarchy problem,
once the parameters are expressed in terms of low-energy observables.Comment: 22 pages, 6 Figure
Antisymmetric Wilson loops in N= 4 SYM: from exact results to non-planar corrections
Indexación: Scopus.A.C. and A.F. were supported by Fondecyt # 1160282. supported by the I.N.F.N., research initiative STEFI.We consider the vacuum expectation values of 1/2-BPS circular Wilson loops in N= 4 super Yang-Mills theory in the totally antisymmetric representation of the gauge group U(N) or SU(N). Localization and matrix model techniques provide exact, but rather formal, expressions for these expectation values. In this paper we show how to extract the leading and sub-leading behavior in a 1/N expansion with fixed ’t Hooft coupling starting from these exact results. This is done by exploiting the relation between the generating function of antisymmetric Wilson loops and a finite-dimensional quantum system known as the truncated harmonic oscillator. Sum and integral representations for the 1/N terms are provided. © 2018, The Author(s).https://link.springer.com/article/10.1007%2FJHEP08%282018%2914
Massive Spinors and dS/CFT Correspondence
Using the map between free massless spinors on d+1 dimensional Minkowski
spacetime and free massive spinors on , we obtain the boundary term
that should be added to the standard Dirac action for spinors in the dS/CFT
correspondence. It is shown that this map can be extended only to theories with
vertex ({\bar\p}\p)^2 but arbitrary . In the case of scalar field
theories such an extension can be made only for with vertices
, and respectively
One-loop Effective Action of the Holographic Antisymmetric Wilson Loop
We systematically study the spectrum of excitations and the one-loop
determinant of holographic Wilson loop operators in antisymmetric
representations of supersymmetric Yang-Mills theory.
Holographically, these operators are described by D5-branes carrying electric
flux and wrapping an in the bulk
background. We derive the dynamics of both bosonic and fermionic excitations
for such D5-branes. A particularly important configuration in this class is the
D5-brane with worldvolume and units of electric flux,
which is dual to the circular Wilson loop in the totally antisymmetric
representation of rank . For this Wilson loop, we obtain the spectrum, show
explicitly that it is supersymmetric and calculate the one-loop effective
action using heat kernel techniques.Comment: 42 pages, one tabl
The Polyakov Loop of Anti-symmetric Representations as a Quantum Impurity Model
The Polyakov loop of an operator in the anti-symmetric representation in N=4
SYM theory on spacial R^3 is calculated, to leading order in 1/N and at large
't Hooft coupling, by solving the saddle point equations of the corresponding
quantum impurity model. Agreement is found with previous results from the
supergravity dual, which is given by a D5-brane in an asymptotically AdS_5 x
S^5 black brane background. It is shown that the azimuth angle, at which the
dual D5-brane wraps the S^5, is related to the spectral asymmetry angle in the
spectral density associated with the Green's function of the impurity fermions.
Much of the calculation also applies to the Polyakov loop on spacial S^3 or
H^3.Comment: 20 pages, 2 figures, v2: references added and small changes in text,
v3: extended to Polyakov loops on spacial R^3, S^3 or H^
Design and performance of the ADMX SQUID-based microwave receiver
The Axion Dark Matter eXperiment (ADMX) was designed to detect ultra-weakly
interacting relic axion particles by searching for their conversion to
microwave photons in a resonant cavity positioned in a strong magnetic field.
Given the extremely low expected axion-photon conversion power we have
designed, built and operated a microwave receiver based on a Superconducting
QUantum Interference Device (SQUID). We describe the ADMX receiver in detail as
well as the analysis of narrow band microwave signals. We demonstrate the
sustained use of a SQUID amplifier operating between 812 and 860 MHz with a
noise temperature of 1 K. The receiver has a noise equivalent power of
1.1x10^-24 W/sqrt(Hz) in the band of operation for an integration time of
1.8x10^3 s.Comment: 8 pages, 12 figures, Submitted to Nuclear Inst. and Methods in
Physics Research,
Spinor Parallel Propagator and Green's Function in Maximally Symmetric Spaces
We introduce the spinor parallel propagator for maximally symmetric spaces in
any dimension. Then, the Dirac spinor Green's functions in the maximally
symmetric spaces R^n, S^n and H^n are calculated in terms of intrinsic
geometric objects. The results are covariant and coordinate-independent.Comment: 7 page
Magnetism in SQUIDs at Millikelvin Temperatures
We have characterized the temperature dependence of the flux threading dc
SQUIDs cooled to millikelvin temperatures. The flux increases as 1/T as
temperature is lowered; moreover, the flux change is proportional to the
density of trapped vortices. The data is compatible with the thermal
polarization of surface spins in the trapped fields of the vortices. In the
absence of trapped flux, we observe evidence of spin-glass freezing at low
temperature. These results suggest an explanation for the "universal" 1/f flux
noise in SQUIDs and superconducting qubits.Comment: 4 pages, 4 figure
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