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A. G. Akeroyd

Publications and source records attributed to A. G. Akeroyd.

At least 55 records · Page 3Linked to original sources
arXiv2006

Multi-photon signatures at the Fermilab Tevatron

Fermiophobic Higgs bosons $h_f$ exhibiting large branching ratios to two photons can arise in models with two or more scalar doublets and/or triplets. In such models the conventional production mechanisms at hadron colliders may be rendered ineffective due to severe mixing angle suppression. In this scenario, double fermiophobic Higgs production may proceed via complementary mechanisms leading to events with up to 4 photons. We perform a simulation of the detection prospects of $h_f$ in the multi-photon (>3) channel at the Fermilab Tevatron and show that a sizeable region of the ($m_{H^\pm},m_{h_f}$) parameter space can be probed during Run II.

hep-ph↗
arXiv2006

CP Studies and Non-Standard Higgs Physics

There are many possibilities for new physics beyond the Standard Model that feature non-standard Higgs sectors. These may introduce new sources of CP violation, and there may be mixing between multiple Higgs bosons or other new scalar bosons. Alternatively, the Higgs may be a composite state, or there may even be no Higgs at all. These non-standard Higgs scenarios have important implications for collider physics as well as for cosmology, and understanding their phenomenology is essential for a full comprehension of electroweak symmetry breaking. This report discusses the most relevant theories which go beyond the Standard Model and its minimal, CP-conserving supersymmetric extension: two-Higgs-doublet models and minimal supersymmetric models with CP violation, supersymmetric models with an extra singlet, models with extra gauge groups or Higgs triplets, Little Higgs models, models in extra dimensions, and models with technicolour or other new strong dynamics. For each of these scenarios, this report presents an introduction to the phenomenology, followed by contributions on more detailed theoretical aspects and studies of possible experimental signatures at the LHC and other colliders.

hep-ph↗
arXiv2005

Single and Pair Production of Doubly Charged Higgs Bosons at Hadron Colliders

Current searches for doubly charged Higgs bosons (H^{\pm\pm}) at the Fermilab Tevatron are sensitive to single production of H^{\pm\pm}, although the pair production mechanism q\bar q\to H^{++}H^{--} is assumed to be dominant. In the context of a Higgs Triplet Model we study the mechanism q'\bar q\to H^{\pm\pm}H^{\mp} at the Tevatron and CERN Large Hadron Collider, and show that its inclusion can significantly improve the search potential for H^{\pm\pm}. Moreover, assuming that the neutrino mass is generated solely by the triplet field Yukawa coupling to leptons, we compare the branching ratios of H^{\pm\pm}\to l^\pm l^\pm and H^{\pm\pm}\to H^\pm W^* for the cases of a normal hierarchical, inverted hierarchical and degenerate neutrino mass spectrum.

hep-ph↗
arXiv2004

Physics Interplay of the LHC and the ILC

Physics at the Large Hadron Collider (LHC) and the International e+e- Linear Collider (ILC) will be complementary in many respects, as has been demonstrated at previous generations of hadron and lepton colliders. This report addresses the possible interplay between the LHC and ILC in testing the Standard Model and in discovering and determining the origin of new physics. Mutual benefits for the physics programme at both machines can occur both at the level of a combined interpretation of Hadron Collider and Linear Collider data and at the level of combined analyses of the data, where results obtained at one machine can directly influence the way analyses are carried out at the other machine. Topics under study comprise the physics of weak and strong electroweak symmetry breaking, supersymmetric models, new gauge theories, models with extra dimensions, and electroweak and QCD precision physics. The status of the work that has been carried out within the LHC / LC Study Group so far is summarised in this report. Possible topics for future studies are outlined.

hep-ph↗
arXiv2004

Double fermiophobic Higgs boson production at the LHC and LC

We consider the phenomenology of a fermiophobic Higgs boson (h_f) at the Large Hadron Collider (LHC) and a e+e- Linear Collider (LC). At both machines the standard production mechanisms which rely on the coupling h_fVV (V=W,Z) can be very suppressed at large tan beta. In such cases the complementary channels pp to H^\pm h_f, A^0 h_f and e+e- to A^0 h_f offer promising cross-sections. Together with the potentially large branching ratios for H^\pm to h_fW* and A^0 to h_fZ*, these mechanisms would give rise to double h_f production, leading to signatures of gamma gamma gamma gamma, gamma gamma VV and VVVV.

hep-ph↗
arXiv2004

Physics at Super B Factory

This report presents the results of studies that investigate the physics reach at a Super B factory, an asymmetric-energy e^+e^- collider with a design luminosity of 5 x 10^35 cm^-2s^-1, which is around 40 times as large as the peak luminosity achieved by the KEKB collider. The studies focus on flavor physics and CP violation measurements that could be carried out in the LHC era. The physics motivation, key observables, measurement methods and expected precisions are presented. The sensitivity studies are a part of the activities associated with the preparation of a Letter of Intent for SuperKEKB, which has been submitted recently.

hep-ex↗
arXiv2003

Effect of H^\pm on D^\pm_s\to μ^\pmνand D^\pm_s\to τ^\pmν

We investigate the effect of a charged Higgs boson (H^\pm) on the decays D^\pm_s\to μ^\pmνand D^\pm_s\to τ^\pmν, which will be measured with high precision at forthcoming CLEO-c. We show that a H^\pm can suppress the branching ratios by 10% \to 15% from the Standard Model prediction, and we emphasize that such contributions should not be overlooked when comparing lattice calculations of f_{D_s} to the values obtained from these decays.

hep-ph↗
arXiv2003

Searching for a very light Higgs boson at the Tevatron

Light Higgs bosons (h^0) with a mass below 60 GeV may have escaped detection at LEP due to a suppressed cross-section for e^+e^-\to Zh^0. Their discovery is also problematic in standard search channels at the Tevatron Run II and LHC. Such a h^0 can arise in the two Higgs doublet model (2HDM) and in the Minimal Supersymmetric Standard Model (MSSM) with explicit CP violating phases. We propose the mechanism p\bar p \to H^\pm h^0 which offers cross-sections of up to 500 fb in the 2HDM, or up to 100 fb in the MSSM. The possibility of a large branching ratio for H^\pm\to h^0W^\pm would give rise to the non-standard signature h^0h^0W^\pm which might facilitate detection.

hep-ph↗
arXiv2003

Neutrino Masses, Baryogenesis and Bilinear R-parity Violation

We consider the impact of cosmological $B-L$ constraints on supersymmetric standard models with bilinear breaking of R-parity. In order to avoid erasing any primordial baryon or lepton asymmetry above the electroweak scale, $B-L$ violation for at least one generation should be sufficiently small. Working in the context of models with non--universal soft supersymmetry breaking masses, we show how the above cosmological constraint can be satisfied while simultaneously providing a neutrino mass matrix required by current data.

hep-ph↗
arXiv2003

The effect of H^\pm on B^\pm -> τ^\pm νand B^\pm -> μ^\pm ν

The hitherto unobserved purely leptonic decays B^\pm -> τ^\pm νand B^\pm -> μ^\pm νare of much interest at current and future runs of the e+e- B factories. Such decays are sensitive to charged Higgs bosons (H^\pm) at the tree-level and provide essentially model independent constraints on \tanβ/m_{H^\pm}. We include the large corrections to the H^\pm-ub coupling induced by virtual SUSY effects and show that the bounds on \tanβ/m_{H^\pm} can be significantly weakened or strengthened.

hep-ph↗
arXiv2002

Large enhancement of D -> e nu and Ds -> e nu in R Parity violating SUSY models

The purely leptonic decays D -> e nu and Ds -> e nu, for which no experimental limits exist, are highly suppressed in the Standard Model. Mere observation of these decays at the B factories BELLE/BaBar or forthcoming CLEO-c would be a clear signal of physics beyond the SM. We show that R parity violating slepton contributions can give rise to spectacular enhancements of the decay rates, resulting in branching ratios as large as 5 x 10^-3, which strongly motivates a search in these channels.

hep-ph↗
arXiv2002

Purely Leptonic B decays at High Luminosity e+e- B factories

High Luminosity upgrades of the KEK-B collider are being discussed. We consider the role of the purely leptonic decays B^\pm -> l^\pm nu and B^0 -> l+l- in motivating such an upgrade. These decays are very sensitive to R parity violating extensions of the MSSM, and we show that future runs of the KEK-B factory can be competitive with high energy colliders for probing such models.

hep-ph↗
arXiv2002

R Parity violating enhancement of Bu -> l nu and Bc -> l nu

We study the decays Bu -> l nu and Bc -> l nu in the context of the Minimal Supersymmetric Standard Model (MSSM) with explicit R parity violation. We analyse the correlation between the two decays and show that branching ratios (BRs) for Bc -> l nu may be of order 5% (over 40% in one case), without violating current bounds on Bu -> l nu. Although Bc mesons are inaccessible at the e+e- B factories, such large BRs for Bc -> l nu would possibly be within experimental observability at LEP and the Tevatron Run II, with much larger yields expected at the hadronic B factories. We also update some earlier bounds on products of R parity violating couplings in the light of new experimental results.

hep-ph↗
arXiv2002

On the possibility of a very light A^0 at low \tanβ

The searches at LEP II for the processes e^+e^-\to h^0Z and e^+e^-\to h^0A^0 in the Minimal Supersymmetric Standard Model (MSSM) fail to exclude regions of the m_h,m_A plane where \tanβ<1, thus allowing a very light A^0 (m_A< 20 GeV). Such a parameter choice would predict a light H^\pm with m_{H^\pm}< m_W. Although the potentially large branching ratio for H^\pm \to A^0 W^* would ensure that H^\pm also escaped detection in direct searches at LEP II and the Tevatron Run I, we show that this elusive parameter space is overwhelmingly disfavoured by electroweak precision measurements.

hep-ph↗
arXiv2002

Supersymmetric enhancement of associated ZA^0 production at e^+e^- colliders

We study the associated production of the A^0 neutral CP-odd Higgs boson with a neutral gauge boson Z in high energy e^+ e^- collisions at the one loop level. We present a detailed discussion for the total cross-section predicted in the context of the Minimal Supersymmetric Standard Model (MSSM) and make a comparison with the non-SUSY Two Higgs Doublet Model (THDM). We show that the MSSM cross-section may be enhanced compared to that for the THDM.

hep-ph↗
arXiv2002

CP-odd Higgs boson production in association with Neutral gauge boson in High-Energy $e^+e^-$ Collisions

We study the associated production of a CP-odd Higgs boson $A^0$ with a neutral gauge boson ($Z$ or photon) in high-energy $e^+ e^-$ collisions at the one-loop level in the framework of Two Higgs Doublet Models (THDM). We find that in the small $\tanβ$ regime the top quark loop contribution is enhanced leading to significant cross-sections (about a few fb), while in the large $\tanβ$ regime the cross-section does not attain observable rates.

hep-ph↗
arXiv2002

Direct CP asymmetry of b -> s gamma and b -> d gamma in models beyond the Standard Model

We study the direct CP asymmetry of the decays b -> s gamma and b -> d gamma in the context of two models: i) a supersymmetric (SUSY) model with unconstrained SUSY phases, and ii) a model with a single generation of vector quarks. In both the above models we show that b -> d gamma can sizeably influence the combined asymmetry (i.e. that of a sample containing both b -> s gamma and b -> d gamma), and in case (ii) may in fact be the dominant contribution.

hep-ph↗