pinecone/core-2020-05-10-deduplication huggingface dataset:
Search for supersymmetry in hadronic final states using MT2 in pp collisions at √s = 7 TeV

Journal of High Energy Physics 2012.10 (2012): 018 reproduced by permission of Scuola Internazionale Superiore di Studi Avanzati (SISSA)Artículo escrito por un elevado número de autores, solo se referencian el que aparece en primer lugar, el nombre del grupo de colaboración, si le hubiere, y los autores pertenecientes a la UAMA search for supersymmetry or other new physics resulting in similar final states is presented using a data sample of 4.73 fb-1 of pp collisions collected at √s = 7TeV with the CMS detector at the LHC. Fully hadronic final states are selected based on the variable MT2, an extension of the transverse mass in events with two invisible particles. Two complementary studies are performed. The first targets the region of parameter space with medium to high squark and gluino masses, in which the signal can be separated from the standard model backgrounds by a tight requirement on MT2. The second is optimized to be sensitive to events with a light gluino and heavy squarks. In this case, the MT2 requirement is relaxed, but a higher jet multiplicity and at least one b-tagged jet are required. No significant excess of events over the standard model expectations is observed. Exclusion limits are derived for the parameter space of the constrained minimal supersymmetric extension of the standard model, as well as on a variety of simplified model spectr
Exact results on the ABJM Fermi gas

We study the Fermi gas quantum mechanics associated to the ABJM matrix model. We develop a method to compute the grand partition function of the ABJM theory, and compute exactly the partition function Z (N) up to N = 9 with the Chern-Simons level k = 1. We find that the eigenvalue problem of this quantum mechanical system is reduced to the diagonalization of a certain Hankel matrix. In reducing the number of integrations by commuting coordinates and momenta, we find an exact relation concerning the grand partition function, which is interesting on its own right and very helpful for determining the partition function. We also study the TBA-type integral equations that allow us to compute the grand partition function numerically. Surprisingly, all of our exact partition functions are written in terms of polynomials of pi(-1) with rational coefficients
QCD in the Color-Flow Representation

For many practical purposes, it is convenient to formulate unbroken
non-abelian gauge theories like QCD in a color-flow basis. We present a new
derivation of SU(N) interactions in the color-flow basis by extending the gauge
group to U(N)xU(1)' in such a way that the two U(1) factors cancel each other.
We use the quantum action principles to show the equivalence to the usual basis
to all orders in perturbation theory. We extend the known Feynman rules to
exotic color representations (e.g. sextets) and interactions (e.g.
$\epsilon_{ijk}$). We discuss practical applications as they occur in automatic
computation programs.Comment: 37 page
Thermalization from gauge/gravity duality: Evolution of singularities in
  unequal time correlators

We consider a gauge/gravity dual model of thermalization which consists of a
collapsing thin matter shell in asymptotically Anti-de Sitter space. A central
aspect of our model is to consider a shell moving at finite velocity as
determined by its equation of motion, rather than a quasi-static approximation
as considered previously in the literature. By applying a divergence matching
method, we obtain the evolution of singularities in the retarded unequal time
correlator $G^R(t,t')$, which probes different stages of the thermalization. We
find that the number of singularities decreases from a finite number to zero as
the gauge theory thermalizes. This may be interpreted as a sign of decoherence.
Moreover, in a second part of the paper, we show explicitly that the thermal
correlator is characterized by the existence of singularities in the complex
time plane. By studying a quasi-static state, we show the singularities at real
times originate from contributions of normal modes. We also investigate the
possibility of obtaining complex singularities from contributions of
quasi-normal modes.Comment: 35 pages, 4 figure
Lattice potentials and fermions in holographic non Fermi-liquids:
  hybridizing local quantum criticality

We study lattice effects in strongly coupled systems of fermions at a finite
density described by a holographic dual consisting of fermions in
Anti-de-Sitter space in the presence of a Reissner-Nordstrom black hole. The
lattice effect is encoded by a periodic modulation of the chemical potential
with a wavelength of order of the intrinsic length scales of the system. This
corresponds with a highly complicated "band structure" problem in AdS, which we
only manage to solve in the weak potential limit. The "domain wall" fermions in
AdS encoding for the Fermi surfaces in the boundary field theory diffract as
usually against the periodic lattice, giving rise to band gaps. However, the
deep infrared of the field theory as encoded by the near horizon AdS2 geometry
in the bulk reacts in a surprising way to the weak potential. The hybridization
of the fermions bulk dualizes into a linear combination of CFT1 "local quantum
critical" propagators in the bulk, characterized by momentum dependent
exponents displaced by lattice Umklapp vectors. This has the consequence that
the metals showing quasi-Fermi surfaces cannot be localized in band insulators.
In the AdS2 metal regime, where the conformal dimension of the fermionic
operator is large and no Fermi surfaces are present at low T/\mu, the lattice
gives rise to a characteristic dependence of the energy scaling as a function
of momentum. We predict crossovers from a high energy standard momentum AdS2
scaling to a low energy regime where exponents found associated with momenta
"backscattered" to a lower Brillioun zone in the extended zone scheme. We
comment on how these findings can be used as a unique fingerprint for the
detection of AdS2 like "pseudogap metals" in the laboratory.Comment: 42 pages, 5 figures; v2, minor correction, to appear in JHE
Measurement of $b$-hadron branching fractions for two-body decays into
  charmless charged hadrons

Based on data corresponding to an integrated luminosity of 0.37 fb^-1
collected by the LHCb experiment in 2011, the following ratios of branching
fractions are measured:
  B(B0 -> pi+ pi-) / B(B0 -> K+pi-) = 0.262 +/- 0.009 +/- 0.017,
  (fs/fd) * B(Bs -> K+K-) / B(B^0 -> K+pi-) = 0.316 +/- 0.009 +/- 0.019,
  (fs/fd) * B(Bs ->pi+ K-) / B(B0 -> K+pi-) = 0.074 +/- 0.006 +/- 0.006,
  (fd/fs) * B(B0 -> K+K-) / B(Bs -> K+K-) = 0.018 {+ 0.008 - 0.007} +/- 0.009,
  (fs/fd) * B(Bs -> pi+pi-) / B(B0 -> pi+pi-) = 0.050 {+ 0.011 - 0.009} +/-
0.004,
  B(Lambda_b -> p pi-) / B(Lambda_b -> p K-) = 0.86 +/- 0.08 +/- 0.05, where
the first uncertainties are statistical and the second systematic. Using the
current world average of B(B0 -> K+pi-) and the ratio of the strange to light
neutral B meson production fs/fd measured by LHCb, we obtain:
  B(B0 -> pi+pi-) = (5.08 +/- 0.17 +/- 0.37) x 10^-6,
  B(Bs -> K+K-) = (23.0 +/- 0.7 +/- 2.3) x 10^-6,
  B(Bs -> pi+K-) = (5.4 +/- 0.4 +/- 0.6) x 10^-6,
  B(B0 -> K+K-) = (0.11 {+ 0.05 - 0.04} +/- 0.06) x 10^-6,
  B(Bs -> pi+pi-) = (0.95 {+ 0.21 - 0.17} +/- 0.13) x 10^-6.
  The measurements of B(Bs -> K+K-), B(Bs -> pi+ K-) and B(B0 -> K+K-) are the
most precise to date. The decay mode Bs -> pi+pi- is observed for the first
time with a significance of more than 5 sigma.Comment: 15 pages, 5 figures, 7 tables; v2 with minor changes after journal
  revie
Conformal field theory of Painlev\'e VI

Generic Painlev\'e VI tau function \tau(t) can be interpreted as four-point
correlator of primary fields of arbitrary dimensions in 2D CFT with c=1. Using
AGT combinatorial representation of conformal blocks and determining the
corresponding structure constants, we obtain full and completely explicit
expansion of \tau(t) near the singular points. After a check of this expansion,
we discuss examples of conformal blocks arising from Riccati, Picard, Chazy and
algebraic solutions of Painlev\'e VI.Comment: 24 pages, 1 figure; v3: added refs and minor clarifications, few
  typos corrected; to appear in JHE
Less Minimal Flavour Violation

We consider the approximate U(2)^3 flavour symmetry exhibited by the quark
sector of the Standard Model and all its possible breaking terms appearing in
the quark Yukawa couplings. Taking an Effective Field Theory point of view, we
determine the current bounds on these parameters, assumed to control the
breaking of flavour in a generic extension of the Standard Model at a reference
scale Lambda. In particular, a significant bound from epsilon'/epsilon is
derived, which is relevant to Minimal Flavour Violation as well. In the
up-quark sector, the recently observed CP violation in D -> pi+ pi-, K+ K-
decays might be accounted for in this generic framework, consistently with any
other constraint.Comment: 15 pages, 1 figur
Beam-helicity asymmetry arising from deeply virtual Compton scattering measured with kinematically complete event reconstruction

The beam-helicity asymmetry in exclusive electroproduction of real photons by the longitudinally polarized HERA positron beam scattering off an unpolarized hydrogen target is measured at HERMES. The asymmetry arises from deeply virtual Compton scattering and its interference with the Bethe-Heitler process. Azimuthal amplitudes of the beam-helicity asymmetry are extracted from a data sample consisting of ep -> ep gamma events with detection of all particles in the final state including the recoiling proton. The installation of a recoil detector, while reducing the acceptance of the experiment, allows the elimination of background from ep -> eN pi gamma events, which was estimated to contribute an average of about 12% to the signal in previous HERMES publications. The removal of this background from the present data sample is shown to increase the magnitude of the leading asymmetry amplitude by 0.054 +/- 0.016 to -0.328 +/- 0.027 (stat.) +/- 0.045 (syst.)
Antenna subtraction at NNLO with hadronic initial states: double real initial-initial configurations

The antenna subtraction method handles real radiation contributions in higher order corrections to jet observables. The method is based on antenna functions, which encapsulate all unresolved radiation between a pair of hard radiator partons. To apply this method to compute hadron collider observables, initial-initial antenna functions with both radiators in the initial state are required in unintegrated and integrated forms. In view of extending the antenna subtraction method to next-to-next-to-leading order (NNLO) calculations at hadron colliders, we derive the full set of initial-initial double real radiation antenna functions in integrated form
On Topologically Massive Spin-2 Gauge Theories beyond Three Dimensions

We investigate in which sense, at the linearized level, one can extend the 3D
topologically massive gravity theory beyond three dimensions. We show that, for
each k=1,2,3... a free topologically massive gauge theory in 4k-1 dimensions
can be defined describing a massive "spin-2" particle provided one uses a
non-standard representation of the massive "spin-2" state which makes use of a
two-column Young tableau where each column is of height 2k-1. We work out the
case of k=2, i.e. 7D, and show, by canonical analysis, that the model
describes, unitarily, 35 massive "spin-2" degrees of freedom. The issue of
interactions is discussed and compared with the three-dimensional situation.Comment: 14 pages. v2: minor changes - published versio
Embedding massive flavor in ABJM

We add massive fundamental matter to the ABJM model by adding D6-branes
wrapped asymptotically over RP3. We find two types of solutions at finite
temperature, one that enters the black hole and one that ends before the black
hole. We analyze the behavior of the free energy as a function of temperature,
and find that the system exhibits a phase transition between the two types of
solutions, similar to what happens in the D3-D7 system. We also analyze the
meson spectrum in the model and find several massive scalar modes, again, quite
like the D3-D7 system. We end with a calculation of the conductivities in the
two phases.Comment: 26 pages, 6 figures; version published in JHE
The large N limit of M2-branes on Lens spaces

We study the matrix model for N M2-branes wrapping a Lens space L(p,1) =
S^3/Z_p. This arises from localization of the partition function of the ABJM
theory, and has some novel features compared with the case of a three-sphere,
including a sum over flat connections and a potential that depends
non-trivially on p. We study the matrix model both numerically and analytically
in the large N limit, finding that a certain family of p flat connections give
an equal dominant contribution. At large N we find the same eigenvalue
distribution for all p, and show that the free energy is simply 1/p times the
free energy on a three-sphere, in agreement with gravity dual expectations.Comment: 28 pages, 4 figure
Exclusive radiative B-meson decays within the aligned two-Higgs-doublet model

In the aligned two-Higgs-doublet model, the alignment of Yukawa matrices in flavour space guarantees the absence of tree-level flavour-changing neutral currents, while allowing at the same time for new sources of CP violation, implying potentially large effects in many low-energy processes. In this work we study the constraints from exclusive radiative $B\to V\gamma$ decays, where $V$ denotes a light vector meson. The current experimental data on the CP-averaged branching ratios and the direct CP and isospin asymmetries are analyzed. It is found that, while the branching ratios and direct CP asymmetries do not constrain the parameter space much further compared to the inclusive $B\to X_{s,d} \gamma$ decays, complementary constraints can be obtained from the isospin asymmetries $\Delta(K^*\gamma)$ and $\Delta(\rho\gamma)$. In addition, correlations between the various observables in exclusive $B\to V\gamma$ and inclusive $B\to X_{s,d} \gamma$ decays are investigated in detail, and predictions are made for several so far unmeasured observables
D-branes in Generalized Geometry and Dirac-Born-Infeld Action

The purpose of this paper is to formulate the Dirac-Born-Infeld (DBI) action
in a framework of generalized geometry and clarify its symmetry. A D-brane is
defined as a Dirac structure where scalar fields and gauge field are treated on
an equal footing in a static gauge. We derive generalized Lie derivatives
corresponding to the diffeomorphism and B-field gauge transformations and show
that the DBI action is invariant under non-linearly realized symmetries for all
types of diffeomorphisms and B-field gauge transformations. Consequently, we
can interpret not only the scalar field but also the gauge field on the D-brane
as the generalized Nambu-Goldstone boson.Comment: 32 pages, 4 figures, ver2:typos corrected, references adde
Cosmology of a Scalar Field Coupled to Matter and an Isotropy-Violating
  Maxwell Field

Motivated by the couplings of the dilaton in four-dimensional effective
actions, we investigate the cosmological consequences of a scalar field coupled
both to matter and a Maxwell-type vector field. The vector field has a
background isotropy-violating component. New anisotropic scaling solutions
which can be responsible for the matter and dark energy dominated epochs are
identified and explored. For a large parameter region the universe expands
almost isotropically. Using that the CMB quadrupole is extremely sensitive to
shear, we constrain the ratio of the matter coupling to the vector coupling to
be less than 10^(-5). Moreover, we identify a large parameter region,
corresponding to a strong vector coupling regime, yielding exciting and viable
cosmologies close to the LCDM limit.Comment: Refs. added, some clarifications. Published in JHEP10(2012)06
Constraining compressed supersymmetry using leptonic signatures

We study the impact of the multi-lepton searches at the LHC on supersymmetric
models with compressed mass spectra. For such models the acceptances of the
usual search strategies are significantly reduced due to requirement of large
effective mass and missing E_T. On the other hand, lepton searches do have much
lower thresholds for missing E_T and p_T of the final state objects. Therefore,
if a model with a compressed mass spectrum allows for multi-lepton final
states, one could derive constraints using multi-lepton searches. For a class
of simplified models we study the exclusion limits using ATLAS multi-lepton
search analyses for the final states containing 2-4 electrons or muons with a
total integrated luminosity of 1-2/fb at \sqrt{s}=7 TeV. We also modify those
analyses by imposing additional cuts, so that their sensitivity to compressed
supersymmetric models increase. Using the original and modified analyses, we
show that the exclusion limits can be competitive with jet plus missing E_T
searches, providing exclusion limits up to gluino masses of 1 TeV. We also
analyse the efficiencies for several classes of events coming from different
intermediate state particles. This allows us to assess exclusion limits in
similar class of models with different cross sections and branching ratios
without requiring a Monte Carlo simulation.Comment: 18 pages, 5 figure
Single-valued harmonic polylogarithms and the multi-Regge limit

We argue that the natural functions for describing the multi-Regge limit of
six-gluon scattering in planar N=4 super Yang-Mills theory are the
single-valued harmonic polylogarithmic functions introduced by Brown. These
functions depend on a single complex variable and its conjugate, (w,w*). Using
these functions, and formulas due to Fadin, Lipatov and Prygarin, we determine
the six-gluon MHV remainder function in the leading-logarithmic approximation
(LLA) in this limit through ten loops, and the next-to-LLA (NLLA) terms through
nine loops. In separate work, we have determined the symbol of the four-loop
remainder function for general kinematics, up to 113 constants. Taking its
multi-Regge limit and matching to our four-loop LLA and NLLA results, we fix
all but one of the constants that survive in this limit. The multi-Regge limit
factorizes in the variables (\nu,n) which are related to (w,w*) by a
Fourier-Mellin transform. We can transform the single-valued harmonic
polylogarithms to functions of (\nu,n) that incorporate harmonic sums,
systematically through transcendental weight six. Combining this information
with the four-loop results, we determine the eigenvalues of the BFKL kernel in
the adjoint representation to NNLLA accuracy, and the MHV product of impact
factors to NNNLLA accuracy, up to constants representing beyond-the-symbol
terms and the one symbol-level constant. Remarkably, only derivatives of the
polygamma function enter these results. Finally, the LLA approximation to the
six-gluon NMHV amplitude is evaluated through ten loops.Comment: 71 pages, 2 figures, plus 10 ancillary files containing analytic
  expressions in Mathematica format. V2: Typos corrected and references added.
  V3: Typos corrected; assumption about single-Reggeon exchange made explici
Bound States of the q-Deformed AdS5 x S5 Superstring S-matrix

The investigation of the q deformation of the S-matrix for excitations on the
string world sheet in AdS5 x S5 is continued. We argue that due to the lack of
Lorentz invariance the situation is more subtle than in a relativistic theory
in that the nature of bound states depends on their momentum. At low enough
momentum |p|<E the bound states transform in the anti-symmetric representation
of the super-algebra symmetry and become the solitons of the Pohlmeyer reduced
theory in the relativistic limit. At a critical momentum |p|=E they become
marginally unstable, and at higher momenta the stable bound states are in the
symmetric representation and become the familiar magnons in the string limit as
q->1. This subtlety fixes a problem involving the consistency of crossing
symmetry with the relativistic limit found in earlier work. With mirror
kinematics, obtained after a double Wick rotation, the bound state structure is
simpler and there are no marginally unstable bound states.Comment: 25 page
Persistent anti-brane singularities

Anti-D-branes inserted in warped throat geometries (supported by fluxes that carry D-brane charges) develop unphysical singularities.It has been argued that these singularities could be resolved when one goes beyond the linearized approximation or includes the effects of brane polarization.In this paper we consider anti-D6 branes, whose singularities have been shown to exist at the full non-linear level, and demonstrate that there is no D8 brane polarization that can resolve the singularity. We comment on the potential implications of this result for the resolution of anti-D3 brane singularities in the Klebanov-Strassler geometry.ANR/08-JCJC-0001-0ERC/String-QCD-BHDFG/EXC/QUESTERC/ObservableStringDFG/WR 166/1-1Alfred P. Sloan FoundationNSF/PHY-075786
Twist analysis of the nucleon spin in QCD

The decomposition of the nucleon spin into that of quarks and gluons is related to twist-two GPDs according to Ji sum rule. Further decomposition into the helicity and the orbital angular momentum inevitably requires twist-three GPDs. In this paper we derive exact relations between twist-three GPDs and the canonical orbital angular momentum density of quarks and gluons, and check their consistency with the longitudinal spin sum rule. Our work demonstrates that the complete decomposition of the nucleon spin fits well with the framework of perturbative QCD
Energy loss in a strongly coupled anisotropic plasma

We study the energy loss of a rotating infinitely massive quark moving, at
constant velocity, through an anisotropic strongly-coupled N=4 plasma from
holography. It is shown that, similar to the isotropic plasma, the energy loss
of the rotating quark is due to either the drag force or radiation with a
continuous crossover from drag-dominated regime to the radiation dominated
regime. We find that the anisotropy has a significant effect on the energy loss
of the heavy quark, specially in the crossover regime. We argue that the energy
loss due to radiation in anisotropic media is less than the isotropic case.
Interestingly this is similar to analogous calculations for the energy loss in
weakly coupled anisotropic plasma.Comment: 26+1 pages, 10 figures, typos fixe
Probing the neutrino mass hierarchy with Super-Kamiokande

We show that for recently discovered large values of theta(13), a superbeam with an average neutrino energy of ~ 5 GeV, such as those being proposed at CERN, if pointing to Super-Kamiokande (L = 8770 km), could reveal the neutrino mass hierarchy at 5 sigma in less than two years irrespective of the true hierarchy and CP phase. The measurement relies on the near resonant matter effect in the numu to nue oscillation channel, and can be done counting the total number of appearance events with just a neutrino beam