[Show abstract][Hide abstract] ABSTRACT: In this note we give recommendations on how to evaluate LHC cross sections
for (neutral) Higgs production and Higgs branching ratios in the general
(CP-conserving) Two-Higgs-Doublet Model (2HDM). The current status of available
higher-order corrections to Higgs production and decay in this model is
discussed, and the existing public codes implementing these calculations are
described. Numerical results are presented for a set of reference scenarios,
demonstrating the very good agreement between the results obtained using
different programs.
[Show abstract][Hide abstract] ABSTRACT: We analyze a model for the Higgs sector with two scalar doublets and a softly
broken $Z_2$ symmetry. One of the doublets breaks the electroweak symmetry and
has tree-level Yukawa couplings to fermions. The other doublet has no vacuum
expectation value and no tree-level couplings to fermions. Because the $Z_2$
parity is broken the two doublets can mix, which leads to a distinct and novel
phenomenology. This Stealth Doublet Model can be seen as a generalization of
the Inert Doublet Model with a broken $Z_2$ symmetry. We outline the model and
present constraints from theory, electroweak precision tests and collider
searches, including the recent observation of a Higgs boson at the LHC. The
CP-odd scalar $A$ and the charged scalar $H^\pm$ couple to fermions at one-loop
level. We compute the decays of $A$ and $H^\pm$ and in particular the one-loop
decays $A \to f \bar{f}$, $H^\pm \to f \bar{f}^\prime $, $H^\pm \to W^\pm Z $
and $H^\pm \to W^\pm \gamma$. We also describe how to calculate and renormalize
such processes in our model. We find that if one of $H^\pm$ or $A$ is the
lightest scalar, $H^\pm \to W^\pm \gamma$ or $ A \to b \bar{b} $ are typically
their respective dominating decay channels. Otherwise, the dominating decays of
$H^\pm$ and $A$ are into a scalar and a vector. Due to the absence of
tree-level fermion couplings for $H^\pm$ and $A$, we consider pair production
and associated production with vector bosons and scalars at the LHC. If the
parameter space of the model that favors $H^\pm \to W^\pm \gamma$ is realized
in Nature, we estimate that there should be a considerable amount of such
events in the present LHC data.
Physical Review D 11/2013; 91(9). DOI:10.1103/PhysRevD.91.095002 · 4.64 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: We consider a model for the Higgs sector with two scalar doublets and a
softly broken Z_2 symmetry, the Stealth Doublet Model. This model can be seen
as a generalization of the Inert Doublet Model. One of the doublets is the
Higgs doublet that participates in electroweak symmetry breaking and couples to
fermions. The other doublet does not couple to fermions at tree level and does
not acquire a vacuum expectation value. The broken Z_2 symmetry leads to
interesting phenomenology such as mixing between the two doublets and charged
and CP-odd scalars that can be light and have unusual decay channels. We
present theoretical and experimental constraints on the model and consider the
recent observation of a Higgs boson at the LHC. The data on the H to
\gamma\gamma\ channel can be naturally accommodated in the model, with either
the lightest or the heaviest CP-even scalar playing the role of the observed
particle.
Journal of High Energy Physics 04/2013; 2013(8). DOI:10.1007/JHEP08(2013)079 · 6.11 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: We analysis the constraints of the general two Higgs doublet models via
evolving the Yukawa coupling constants to high energy under renormalization
group. We consider the appearance of a Landau pole or large off-diagonal Yukawa
couplings which cause tree level flavour changing neutral currents. Our study
shows the latter condition can be used to answer that how much $Z_2$ symmetry
breaking can be allowed in a given 2HDM model.
[Show abstract][Hide abstract] ABSTRACT: We revisit diffractive and exclusive W production at hadron colliders in
different models for soft colour exchanges. The process pp to p[WX]p, and in
particular a W charge asymmetry, has been suggested as a way to discriminate
diffractive processes as being due to pomeron exchange in Regge phenomenology
or QCD-based colour reconnection models. Our detailed analysis of the latter
models at LHC energies shows, however, that they give similar results as
pomeron models for very leading protons and central W production, including a
vanishing W charge asymmetry. We demonstrate that soft colour exchange models
provide a continuous transition from diffractive to inelastic processes and
thereby include the intrinsic asymmetry of inelastic interactions while being
at the same time sensitive to the underlying hadronisation models. Such
sensitivity also concerns the differential distributions in proton momentum and
W transverse momentum which opens possibilities to discriminate between
different colour reconnection models.
[Show abstract][Hide abstract] ABSTRACT: In the Next-to-Minimal SuperSymmetric Model (NMSSM) the lightest CP-odd Higgs
bosons (a1) can be very light. As a consequence, in addition to the standard
charged Higgs boson (h+) decays considered in the MSSM for a light charged
Higgs (m_h+ < m_t), the branching fraction for h+ to a1 W can be dominant. We
investigate how this signal can be searched for in t tbar production at the
Large Hadron Collider (LHC) in the case that m_a1 \gtrsim 2m_B with the a1
giving rise to a single b bbar-jet and discuss to what extent the LHC
experiments are able to discover such a scenario with an integrated luminosity
\sim 20 fb-1. We also discuss the implications of the possible Higgs-signal
observed at the LHC.
Advances in High Energy Physics 06/2012; 2012(2). DOI:10.1155/2012/853706 · 2.20 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: We study how general two Higgs doublet models can be constrained by
considering their properties under renormalization group evolution of the
Yukawa couplings. We take into account both the appearance of a Landau pole as
well as off-diagonal Yukawa couplings leading to flavour changing neutral
currents in violation with experimental constraints at the electroweak scale.
We find that the latter condition can be used to limit the amount of Z2
symmetry breaking allowed in a given model.
Journal of High Energy Physics 11/2011; 2012(5). DOI:10.1007/JHEP05(2012)118 · 6.11 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The Jewel 1.0 Monte Carlo simulates jet evolution in a medium with a microscopic description of splitting and scattering processes.
In the framework of this model we investigate the transverse momentum broadening due to medium effects in different scenarios.
Depending on assumptions about hadronisation, we observe either a small increase or even a slight decrease of the mean transverse
momentum, but no sizeable broadening. This appears to be a natural consequence of a model formulation which conserves energy
and momentum microscopically at each splitting and at each scattering.
KeywordsJet quenching–dihadron correlations
Indian Journal of Physics 07/2011; 85(7):1033-1038. DOI:10.1007/s12648-011-0145-0 · 1.38 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: We present the program 2HDMC and how it can be used to explore the physics of
general CP conserving two Higgs doublet models.
[Show abstract][Hide abstract] ABSTRACT: New fundamental particles, charged under new gauge groups and only weakly
coupled to the standard sector, could exist at fairly low energy scales. In
this article we study a selection of such models, where the secluded group
either contains a softly broken U(1) or an unbroken SU(N). In the Abelian case
new {\gamma}v gauge bosons can be radiated off and decay back into visible
particles. In the non-Abelian case there will not only be a cascade in the
hidden sector, but also hadronization into new {\pi}v and {\rho}v mesons that
can decay back. This framework is developed to be applicable both for e+e- and
pp collisions, but for these first studies we concentrate on the former process
type. For each Abelian and non-Abelian group we study three different scenarios
for the communication between the standard sector and the secluded one. We
illustrate how to distinguish the various characteristics of the models and
especially study to what extent the underlying gauge structure can be
determined experimentally.
Journal of High Energy Physics 02/2011; 2011(4). DOI:10.1007/JHEP04(2011)091 · 6.11 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: We consider scenarios in the next-to-minimal supersymmetric model (NMSSM)
where the CP-odd and charged Higgs bosons are very light. As we demonstrate,
these can be obtained as simple deformations of existing phenomenological MSSM
benchmarks scenarios with parameters defined at the weak scale. This offers a
direct and meaningful comparison to the MSSM case. Applying a wide set of
up-to-date constraints from both high-energy collider and flavour physics, the
Higgs boson masses and couplings are studied in viable parts of parameter
space. The LHC phenomenology of the light Higgs scenario for neutral and
charged Higgs boson searches is discussed.
European Physical Journal C 12/2010; 71(4). DOI:10.1140/epjc/s10052-011-1608-3 · 5.08 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: At the Large Hadron Collider, we prove the feasibility to detect pair production of the lightest CP-even Higgs boson h of a Type II 2-Higgs Doublet Model through the process q \bar q' --> Vhh (Higgs-strahlung, V=W+-,Z), in presence of two h --> b \bar b decays. We also show that, through such production and decay channels, one has direct access to the following Higgs self-couplings, thus enabling one to distinguish between a standard and the Supersymmetric version of the above model: lambda_(Hhh) -- which constrains the form of the Higgs potential -- as well as lambda_(W+- H+- h) and lambda_(Z A h) -- which are required by gauge invariance. Unfortunately, such claims cannot be extended to the Minimal Supersymmetric Standard Model, where the extraction of the same signals is impossible. Comment: Added one figure, few references and minor corrections to the text. Results unchanged
Journal of High Energy Physics 08/2010; 2010(11). DOI:10.1007/JHEP11(2010)097 · 6.11 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: On page 196 in the original 2HDMC publication [the authors, “2HDMC – two-Higgs-doublet model calculator”, ibid. 181, No. 1, 189–205 (2010; Zbl 1205.82016)], the normalization factors in the expressions for the oblique parameters were reported correctly. The correct expressions should read S=1 24π{⋯},T=1 16πsin 2 θ w m w 2 {⋯},U=1 24π{⋯}, in order to correspond to what is calculated by the code. The contents of the large parentheses are left unchanged from the expressions in [the authors, loc. cit.].
[Show abstract][Hide abstract] ABSTRACT: This manual describes the public code 2HDMC which can be used to perform calculations in a general, CP-conserving, two-Higgs-doublet model (2HDM). The program features simple conversion between different parametrizations of the 2HDM potential, a flexible Yukawa sector specification with choices of different Z_2-symmetries or more general couplings, a tree-level decay library including all two-body - and some three-body - decay modes for the Higgs bosons, and the possibility to calculate observables of interest for constraining the 2HDM parameter space, as well as theoretical constraints from positivity and unitarity. The latest version of the 2HDMC code and full documentation is available from: http://www.isv.uu.se/thep/MC/2HDMC Comment: 28 pages, no figures. Minor changes to the text, new interface to HiggsBounds described. Agrees with published version
[Show abstract][Hide abstract] ABSTRACT: We present a new model, based on color rearrangements, which at the same time can describe both hidden and open charm production in B-meson decays. The model is successfully compared to both inclusive decays, such as B -> J / psi X and B -> D(s)X, as well as exclusive ones, such as B -> J / psi K((*)) and B -> D((*))D((*))K. It also gives a good description of the momentum distribution of direct J / psi's, especially in the low-momentum region, which earlier has been claimed as a possible signal for new exotic states.
[Show abstract][Hide abstract] ABSTRACT: We investigate the viability of observing charged Higgs bosons (H ± ) produced in association with W bosons at the CERN Large Hadron Collider, using the leptonic decay H + → τ + ντ and hadronic W decay, within the Minimal Supersymmetric Standard Model. Performing a parton level study we show how the irreducible Standard Model background from W + 2 jets can be controlled by applying appropriate cuts. In the standard m max h scenario we find a viable signal for large tan β and intermediate H ± masses ( ∼ mt). The quest for understanding electroweak symmetry breaking and mass generation is one of the driving forces behind the upcoming experiments at the CERN Large Hadron Collider (LHC). In the Minimal Supersymmetric Standard Model (MSSM), which is a two Higgs Doublet Model (2HDM) of type II, the Higgs sector consists of three neutral and one charged Higgs bosons after electroweak symmetry breaking. The charged Higgs boson (H±) is of special interest since its discovery would constitute an indisputable proof of physics beyond the Standard Model. The main production mode of charged Higgs bosons at hadron colliders is in association with top quarks through the gb → H−t and gg → H−t¯b processes [1–4] with the former one
Journal of Physics Conference Series 06/2008; 110(7):072008. DOI:10.1088/1742-6596/110/7/072008
[Show abstract][Hide abstract] ABSTRACT: We have developed the Monte Carlo simulation program JEWEL 1.0 (Jet Evolution With Energy Loss), which interfaces a perturbative final state parton shower with medium effects occurring in ultra-relativistic heavy ion collisions. This is done by comparing for each jet fragment the probability of further perturbative splitting with the density-dependent probability of scattering with the medium. A simple hadronisation mechanism is included. In the absence of medium effects, we validate JEWEL against a set of benchmark jet measurements. For elastic interactions with the medium, we characterise not only the medium-induced modification of the jet, but also the jet-induced modification of the medium. Our main physics result is the observation that collisional and radiative medium modifications lead to characteristic differences in the jet fragmentation pattern, which persist above a soft background cut. We argue that this should allow to disentangle collisional and radiative parton energy loss mechanisms by measuring the n-jet fraction or a class of jet shape observables.
European Physical Journal C 05/2008; 60(4). DOI:10.1140/epjc/s10052-009-0941-2 · 5.08 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: This writeup is a compilation of the predictions for the forthcoming Heavy Ion Program at the Large Hadron Collider, as presented at the CERN Theory Institute 'Heavy Ion Collisions at the LHC - Last Call for Predictions', held from 14th May to 10th June 2007.
Journal of Physics G Nuclear and Particle Physics 05/2008; 35(5). DOI:10.1088/0954-3899/35/5/054001 · 2.78 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Report of the Working Group on Higgs Bosons for the Workshop, ``Physics at
TeV Colliders'', Les Houches, France, 11-29 June, 2007.
Les Houches Physics at Tev Colliders, Les Houches, France, 2007; 03/2008