J. Santiago - Departamento de Astrofisica y Ciencias de la Atmosfera, Facultad de Ciencias Fisicas, Universidad Complutense de Madrid, Madrid, Spain

J. Santiago
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J. Santiago
Departamento de Astrofisica y Ciencias de la Atmosfera, Facultad de Ciencias Fisicas, Universidad Complutense de Madrid, Madrid, Spain

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High Energy Physics - Phenomenology (34)
High Energy Physics - Experiment (17)
High Energy Physics - Theory (4)
Solar and Stellar Astrophysics (3)
Physics - Statistical Mechanics (3)
Astrophysics of Galaxies (3)
General Relativity and Quantum Cosmology (3)
Mathematics - Mathematical Physics (2)
Physics - Soft Condensed Matter (2)
Instrumentation and Methods for Astrophysics (2)
Mathematical Physics (2)
Physics - General Physics (1)
Physics - Fluid Dynamics (1)
Mathematics - Classical Analysis and ODEs (1)
Computer Science - Networking and Internet Architecture (1)

Publications Authored By J. Santiago

So-called "twisted" black holes have recently been proposed by Zhang (1609.09721 [gr-qc]), and further considered by Chen and Jing (1610.00886 [gr-qc]), and more recently by Ong (1610. Read More

Far as we know there are not exact solutions to the equation of motion for a relativistic harmonic oscillator. In this paper, the relativistic harmonic oscillator equation which is a nonlinear ordinary differential equation is studied by means of a combined use of the Adomian Decomposition Method and the Laplace Transform (LADM). The results that we have obtained, a series of powers of functions, have never been reported and show a very good match when compared with other approximate solutions, obtained by different methods. Read More

We present the activities of the 'New Physics' working group for the 'Physics at TeV Colliders' workshop (Les Houches, France, 1-19 June, 2015). Our report includes new physics studies connected with the Higgs boson and its properties, direct search strategies, reinterpretation of the LHC results in the building of viable models and new computational tool developments. Important signatures for searches for natural new physics at the LHC and new assessments of the interplay between direct dark matter searches and the LHC are also considered. Read More

Extensions of the Standard Model Higgs sector with electroweak charged scalars can possess exotic `Higgs' bosons with vanishing or suppressed couplings to Standard Model fermions. These `fermiophobic' scalars, which cannot be produced via gluon fusion, are constrained by LHC measurements of the 125 GeV Higgs boson to have a small vacuum expectation value. This implies that vector boson fusion and associated vector boson production are in general suppressed rendering conventional Higgs searches insensitive. Read More

We discuss the limitations of the covariant derivative expansion prescription advocated to compute the one-loop Standard Model (SM) effective lagrangian when the heavy fields couple linearly to the SM. In particular, one-loop contributions resulting from the exchange of both heavy and light fields must be explicitly taken into account through matching because the proposed functional approach alone does not account for them. We review a simple case with a heavy scalar singlet of charge $-1$ to illustrate the argument. Read More

We consider the possibility that the recently observed diphoton excess at $\sim 750$ GeV can be explained by the decay of a scalar particle ($\varphi$) to photons. If the scalar is the remnant of a symmetry-breaking sector of some new gauge symmetry, its coupling to photons can be generated by loops of the charged massive vectors of the broken symmetry. If these new $W^\prime$ vector bosons carry color, they can also generate an effective coupling to gluons. Read More

Pair production of new vector-like quarks in $pp$ collisions is considered model independent as it is usually dominated by QCD production. Nonetheless, the presence of a new massive color octet (heavy gluon) in some composite Higgs models may modify the pair production rate of vector-like quarks. This scenario is considered and the possible differences between the usual QCD production and the production mediated via heavy gluons is studied. Read More

We examine the `diboson' excess at $\sim 2$ TeV seen by the LHC experiments in various channels. We provide a comparison of the excess significances as a function of the mass of the tentative resonance and give the signal cross sections needed to explain the excesses. We also present a survey of available theoretical explanations of the resonance, classified in three main approaches. Read More

We investigate the stability of a free scalar field nonminimally coupled to gravity under linear perturbations in the spacetime of a charged spherical shell. Our analysis is performed in the context of quantum field theory in curved spacetimes. This paper completes previous analyses which considered the exponential enhancement of vacuum fluctuations in the spacetime of massive shells. Read More

A UFO model describing general top quark Flavour Changing Neutral Currents is presented. We use it to study t$\gamma$, tH and tZ production via FCNCs anomalous couplings at the Large Hadron Collider, in particular how the distributions of physical observables depend on the anomalous couplings. A sensitivity study of the Large Hadron Collider experiments to tZ production via FCNC in its second stage of operation is also performed. Read More

Pair production of new vector-like quarks in pp collisions is considered model independent as it is usually dominated by QCD production. We discuss the interpretation of vector-like quark searches in the case that QCD is not the only relevant production mechanism for the new quarks. In particular we consider the effect of a new massive color octet vector boson with sizeable decay branching ratio into the new quarks. Read More

We show that the recently reported excess in resonant diboson production can be explained in the context of non-custodial composite Higgs models. Dibosons are generated via the s-channel exchange of massive vector bosons present in these models. We discuss the compatibility of the signal excess with other diboson experimental searches. Read More

Anomalous interactions involving the top quark contribute to some of the most difficult observables to directly access experimentally. They can give however a sizeable correction to very precisely measured observables at the loop level. Using a model-independent effective Lagrangian approach, we present the leading indirect constraints on dimension-six effective operators involving the top quark from electroweak precision data. Read More

Many Standard Model extensions can contribute to four-lepton signals at large colliders. We review the particular case of leptophilic interactions eventually observable at the LHC and the ILC, paying special attention to the addition of a new vector boson coupled to muon minus tau lepton number, $Z'_{\mu - \tau}$, and emphasizing the prospects at a very large hadron collider with $\sqrt s =$ 100 TeV. We also discuss in this case the new contribution to two-lepton (Drell-Yan) production when the new leptophilic interaction has a non-vanishing kinetic mixing with the SM. Read More

We consider a microfluidic mixer based on hydrodynamic focusing, which is used to initiate the folding process of individual proteins. The folding process is initiated by quickly diluting a local denaturant concentration, and we define mixing time as the time advecting proteins experience a specified to achieve a local drop in denaturant concentration. In previous work, we presented a minimization of mixing time which considered optimal geometry and flow conditions, and achieved a design with a predicted mixing time of 0. Read More

We classify all possible new scalar particles that can have renormalizable linear couplings to Standard Model fields and therefore be singly produced at colliders. We show that this classification exhausts the list of heavy scalar particles that contribute at the tree level to the Standard Model effective Lagrangian to dimension six. We compute this effective Lagrangian for a general scenario with an arbitrary number of new scalar particles and obtain flavor-preserving constraints on their couplings and masses. Read More

Leptophilic interactions can only be observed at the LHC in four-lepton final states. If these interactions are mediated by a resonance in the di-leptonic channel with renormalizable couplings, the mediator must have spin 1. We study the LHC reach for such a vector boson allowing for arbitrary couplings. Read More

We study the phenomenology of vector resonances in the context of natural composite Higgs models. A mild hierarchy between the fermionic partners and the vector resonances can be expected in these models based on the following arguments. Both direct and indirect (electroweak and flavor precision) constraints on fermionic partners are milder than the ones on spin one resonances. Read More

We define a lepton-based asymmetry in semi-leptonic ttbar production at the LHC. We show that the ratio of this lepton-based asymmetry and the ttbar charge asymmetry, measured as a function of the lepton transverse momentum or the ttbar invariant mass is a robust observable in the Standard Model. It is stable against higher order corrections and mis-modeling effects. Read More

Key Performance Indicators (KPIs) are widely used by GSM and UMTS carriers with the aim of evaluating the network performance and the Quality of Service (QoS) delivered to users. TETRA networks are basically designed to provide telecommunication services to Public Safety & Security (PSS) organizations, thus the compliance of the QoS levels required by these clients is usually critical. Despite that, the use of KPIs to assess the network performance and the QoS achieved in TETRA systems is not very common. Read More

The Large Hadron Collider can do precision physics at a level that is competitive with electroweak precision constraints when probing physics beyond the Standard Model. We present a simple yet general parameterization of the effect of an arbitrary number of lepton-quark contact interactions on any di-lepton observable at hadron colliders. This parameterization can be easily adopted by the experimental collaborations to put bounds on arbitrary combinations of lepton-quark contact interactions. Read More

New vector-like quarks with electric charge 2/3 and -1/3 can be singly produced at hadron colliders through the exchange of a color octet vector resonance in models of strong electroweak symmetry breaking. We show that electroweak symmetry breaking effects can have a significant impact on the decay pattern of these new quarks. In particular, single production of charge -1/3 fermion resonances, mediated by a color octet vector resonance, typically results in an $H b\bar{b}$ final state with a sizeable cross section and very distinctive kinematics. Read More

We discuss some aspects of the interplay between the top quark and the Higgs boson at the LHC. First we describe what indirect information on the top Yukawa coupling can be extracted from measurements in the Higgs sector. We then show that the study of processes involving $Ht\bar{t}$ and $Hb\bar{b}$ final states can give us information on the spectrum in models of strong electroweak symmetry breaking. Read More

New vector-like quarks can mix sizably with first generation Standard Model quarks without conflicting with current experimental constraints. Searches for such new quarks have been performed in pair production and electroweak single production channels with subsequent decays into electroweak gauge bosons. To fully explore the underlying structure of the theory the channels with heavy quark decays into Higgs bosons are crucial and in this article we consider for the first time the LHC reach for such channels. Read More

Using classical differential geometry, the problem of elastic curves and surfaces in the presence of long-range interactions $\Phi$, is posed. Starting from a variational principle, the balance of elastic forces and the corresponding projections ${\bf n}_i\cdot \nabla\Phi$, are found. In the case of elastic surfaces, a force coupling the mean curvature with the external potential, $K\Phi$, appears; it is also present in the shape equation along the normal principal in the case of curves. Read More

The bending energy of any freely deformable closed surface is quadratic in its curvature. In the absence of constraints, it will be minimized when the surface adopts the form of a round sphere. If the surface is confined within a hypersurface of smaller size, however, this spherical state becomes inaccessible. Read More

Composite Higgs models are only now starting to be probed at the Large Hadron Collider by Higgs searches. We point out that new resonances, abundant in these models, can mediate new production mechanisms for the composite Higgs. The new channels involve the exchange of a massive color octet and single production of new fermion resonances with subsequent decays into the Higgs and a Standard Model quark. Read More

Authors: G. Brooijmans, B. Gripaios, F. Moortgat, J. Santiago, P. Skands, D. Albornoz Vásquez, B. C. Allanach, A. Alloul, A. Arbey, A. Azatov, H. Baer, C. Balázs, A. Barr, L. Basso, M. Battaglia, P. Bechtle, G. Bélanger, A. Belyaev, K. Benslama, L. Bergström, A. Bharucha, C. Boehm, M. Bondarenko, O. Bondu, E. Boos, F. Boudjema, T. Bringmann, M. Brown, V. Bunichev, S. Calvet, M. Campanelli, A. Carmona, D. G. Cerdeño, M. Chala, R. S. Chivukula, D. Chowdhury, N. D. Christensen, M. Cirelli, S. Cox, K. Cranmer, J. Da Silva, T. Delahaye, A. De Roeck, A. Djouadi, E. Dobson, M. Dolan, F. Donato, G. Drieu La Rochelle, G. Duda, C. Duhr, B. Dumont, J. Edsjö, J. Ellis, C. Evoli, A. Falkowski, M. Felcini, B. Fuks, E. Gabrielli, D. Gaggero, S. Gascon-Shotkin, D. K. Ghosh, A. Giammanco, R. M. Godbole, P. Gondolo, T. Goto, D. Grasso, P. Gris, D. Guadagnoli, J. F. Gunion, U. Haisch, L. Hartgring, S. Heinemeyer, M. Hirsch, J. Hewett, A. Ismail, T. Jeltema, M. Kadastik, M. Kakizaki, K. Kannike, S. Khalil, J-L. Kneur, M. Krämer, S. Kraml, S. Kreiss, J. Lavalle, R. Leane, J. Lykken, L. Maccione, F. Mahmoudi, M. Mangano, S. P. Martin, D. Maurin, G. Moreau, S. Moretti, I. Moskalenko, G. Moultaka, M. Muhlleitner, I. Niessen, B. O'Leary, E. Orlando, P. Panci, G. Polesello, W. Porod, T. Porter, S. Profumo, H. Prosper, A. Pukhov, A. Racioppi, M. Raidal, M. Rausch de Traubenberg, A. Renaud, J. Reuter, T. G. Rizzo, T. Robens, A. Y. Rodríguez-Marrero, P. Salati, C. Savage, P. Scott, S. Sekmen, A. Semenov, C. -L. Shan, C. Shepherd-Themistocleous, E. H. Simmons, P. Slavich, C. Speckner, F. Staub, A. Strong, R. Taillet, F. S. Thomas, M. C. Thomas, I. Tomalin, M. Tytgat, M. Ughetto, L. Valéry, D. G. E. Walker, A. Weiler, S. M. West, C. D. White, A. J. Williams, A. Wingerter, C. Wymant, J. -H. Yu, C. -P. Yuan, D. Zerwas

We present the activities of the "New Physics" working group for the "Physics at TeV Colliders" workshop (Les Houches, France, 30 May-17 June, 2011). Our report includes new agreements on formats for interfaces between computational tools, new tool developments, important signatures for searches at the LHC, recommendations for presentation of LHC search results, as well as additional phenomenological studies. Read More

New colour octet vectors below the TeV scale could explain the anomalous t tbar forward-backward asymmetry observed at the Tevatron experiments, while being consistent with the current LHC data. These models generally lead to four-top final states at the LHC at observable levels. We compute the four-top production cross section at the LHC in a model with a massive colour octet vector as a function its mass, its width and its coupling to the top quark. Read More

A general action for particles faster than light is presented. It is demonstrated that this action is invariant under reparametrizations. For several cases, it is shown that in the high velocity regime the action is invariant under anisotropic space-time transformation and at quantum level the system has fractal behavior. Read More

A gluon resonance G of mass below 1 TeV could be the origin of the t\bar{t} forward-backward asymmetry observed at the Tevatron provided that new decay modes G->\bar{q}Q, with q a standard quark and Q its massive excitation, make G broad enough. We consider all the different cases, with q the top, the bottom or a light quark and dominant decay modes Q->Wq' or Q->Zq. We show that current experimental searches are unable to probe the model, but that minimal departures from these analyses can explore a large region of its parameter space for the current LHC luminosity. Read More

We compute the dimension 6 effective Lagrangian arising from the tree level integration of an arbitrary number of bulk fermions in models with warped extra dimensions. The coefficients of the effective operators are written in terms of simple integrals of the metric and are valid for arbitrary warp factors, with or without an infrared brane, and for a general Higgs profile. All relevant tree level fermion effects in electroweak and flavor observables can be computed using this effective Lagrangian. Read More

We analyze a one-component simple fluid in a liquid-vapor coexistence state, which forms an arbitrarily curved interface. By using an approach based on density functional theory, we obtain an exact and simple expression for the grand potential at the level of mean field approximation that depends on the density profile and the short-range interaction potential. By introducing the step-function approximation for the density profile, and using general geometric arguments, we expand the grand potential in powers of the principal curvatures of the surface and find consistency with the Helfrich phenomenological model in the second order approximation. Read More

We study the effect of bulk fermions on electroweak precision observables in a recently proposed model with warped extra dimensions and no custodial symmetry. We find that the top-quark mass, together with the corrections to the Zbb vertex and the one-loop contribution to the T parameter, which is finite, impose important constraints that single out a well defined region of parameter space. New massive vector bosons can be as light as 1. Read More

We find that a heavy gluon G of mass 800-900 GeV with small, mostly axial-vector couplings to the light quarks and relatively large vector and axial-vector couplings to the top quark can explain the t \bar{t} forward-backward asymmetry observed at the Tevatron with no conflict with other top-quark or dijet data. The key ingredient is a complete treatment of energy-dependent width effects and a new decay mode G->qQ, where q is a standard quark and Q a vector-like quark of mass 400--600 GeV. We show that this new decay channel makes the heavy gluon invisible in the t\bar{t} mass invariant distribution and discuss its implications at the Tevatron and the LHC. Read More

We argue that a relatively light massive gluon with mass <= 1 TeV, small purely axial couplings to light quarks and sizable vector and axial couplings to the top quark can reproduce the large forward-backward asymmetry observed at the Tevatron without conflicting with the t tbar and the dijet invariant mass distributions measured at the Tevatron and the LHC. We show that realistic Higgsless models with warped extra dimensions naturally fulfil all the necessary ingredients to realize this scenario. While current data is unable to discover or exclude these heavy gluons with masses 850 GeV, they should be observed at the (7 TeV) LHC with a luminosity of the order of 300 pb^{-1}. Read More

Models with warped extra dimensions, and their strongly coupled duals, offer a nice solution to the hierarchy problem and a very appealing realisation of flavour. Compatibility with the very stringent electroweak and flavour tests have made a generic picture emerge, with a composite Higgs, partial compositeness and custodial symmetry as the main ingredients. We review the main features of this picture and discuss how -and when- models with warped extra dimensions could be discovered at the Large Hadron Collider. Read More

New vector-like quarks can have sizable couplings to first generation quarks without conflicting with current experimental constraints. The coupling with valence quarks and unique kinematics make single production the optimal discovery process. We perform a model-independent analysis of the discovery reach at the Large Hadron Collider for new vector-like quarks considering single production and subsequent decays via electroweak interactions. Read More

We present the report of the hadronic working group of the BOOST2010 workshop held at the University of Oxford in June 2010. The first part contains a review of the potential of hadronic decays of highly boosted particles as an aid for discovery at the LHC and a discussion of the status of tools developed to meet the challenge of reconstructing and isolating these topologies. In the second part, we present new results comparing the performance of jet grooming techniques and top tagging algorithms on a common set of benchmark channels. Read More

Using Environmentally Friendly Renormalization, we present an analytic calculation of the series for the renormalization constants that describe the equation of state for the $O(N)$ model in the whole critical region. The solution of the beta-function equation, for the running coupling to order two loops, exhibits crossover between the strong coupling fixed point, associated with the Goldstone modes, and the Wilson-Fisher fixed point. The Wilson functions $\gamma_\lambda$, $\gamma_\phi$ and $\gamma_{\phi^2}$, and thus the effective critical exponents associated with renormalization of the transverse vertex functions, also exhibit non-trivial crossover between these fixed points. Read More

The tau lepton can be more composite than naively expected in models of strong electroweak symmetry breaking with tri-bimaximal lepton mixing. New leptonic resonances required by custodial symmetry, the tau custodians, can then be the first signal of this lepton flavor realization. Tau custodians can be very light, decaying almost exclusively into taus. Read More

We study an electrodynamics consistent with anisotropic transformations of space-time with an arbitrary dynamic exponent $z$. The equations of motion and conserved quantities are explicitly obtained. We show that the propagator of this theory can be regarded as a quantum correction to the usual propagator. Read More

In the framework of the Water in Star-forming regions with Herschel (WISH) key program, maps in water lines of several outflows from young stars are being obtained, to study the water production in shocks and its role in the outflow cooling. This paper reports the first results of this program, presenting a PACS map of the o-H2O 179 um transition obtained toward the young outflow L1157. The 179 um map is compared with those of other important shock tracers, and with previous single-pointing ISO, SWAS, and Odin water observations of the same source that allow us to constrain the water abundance and total cooling. Read More

We briefly summarise the current status of neutrino masses and mixing, paying special attention to the prospects for observing new leptonic interactions. Read More

We show that holographic composite Higgs Models with a discrete A4 symmetry naturally predict hierarchical charged lepton masses and an approximate tri-bimaximal lepton mixing with the correct scale of neutrino masses. They also satisfy current constraints from electroweak precision tests, lepton flavor violation and lepton mixing in a large region of parameter space. Two phenomenologically relevant features arise in these models. Read More

The Large Hadron Collider presents an unprecedented opportunity to probe the realm of new physics in the TeV region and shed light on some of the core unresolved issues of particle physics. These include the nature of electroweak symmetry breaking, the origin of mass, the possible constituent of cold dark matter, new sources of CP violation needed to explain the baryon excess in the universe, the possible existence of extra gauge groups and extra matter, and importantly the path Nature chooses to resolve the hierarchy problem - is it supersymmetry or extra dimensions. Many models of new physics beyond the standard model contain a hidden sector which can be probed at the LHC. Read More

We report the discovery of three new variable stars in Indus: USNO-B1.0 0311-0760061, USNO-B1.0 0309-0771315, and USNO-B1. Read More