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A. G. Akeroyd

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

70 records · Page 4Linked to original sources
arXiv2001

Direct CP Asymmetry of B -> X_d,s γin a model with Vector quarks

We investigate the effect of vector quarks on the inclusive decays B -> X_d,s γ. We show that the branching ratio of B -> X_d γcan differ sizably from the SM and MSSM predictions, being enhanced to present experimental observability or suppressed such that present runs of the B factories would not observe it. Current measurements of the direct CP asymmetry (A_CP) for B -> X_s γare sensitive to the contribution from B -> X_d γ. For a sufficiently enhanced BR(B -> X_d γ) we show that the dominant contribution to the combined asymmetry may be from B -> X_d γ. Thus any large value for A_CP should not immediately be attributed to B -> X_s γ, which stresses the importance of good K/pi separation.

hep-ph↗
arXiv2001

Large mass splittings between charged and neutral Higgs bosons in the MSSM

We show that large ($> 100$ GeV) mass splittings between the charged Higgs boson ($H^\pm$) and the neutral Higgs bosons ($H^0$ and $A^0$) are possible in the Minimal Supersymmetric Standard Model (MSSM). Such splittings occur when the $μ$ parameter is considerably larger than the common SUSY scale, $M_{SUSY}$, and have significant consequences for MSSM Higgs searches at future colliders.

hep-ph↗
arXiv2001

Stau LSP and comparison with H^+(-) phenomenology

In supersymmetric models with explicit breaking of R-parity the lightest supersymmetric particle (LSP) may be the lightest stau, $\stau_1$. Such a scenario would provide a clear sign of R-parity violating SUSY, although its phenomenology may resemble that of a charged Higgs boson, $H^\pm$. We discuss various ways of distinguishing a LSP $\stau_1$ from $H^\pm$ at future colliders, and address the case of $\stau_1$ mimicking the signal for $H^\pm$. As an example we suggest that the recent L3 signal for $H^+H^-\to qq'qq'$ and $H^+H^-\to qq'τν_τ$ could be more easily explained by a LSP $\stau_1$.

hep-ph↗
arXiv2001

Probing scalar-pseudoscalar mixing in the CP violating MSSM at high-energy $e^+e^-$ colliders

We study the production processes $e^+e^-\to H^0_iZ$, $H^0_iH^0_j$ and $H^0_iν_e\overline ν_e$ in the context of the CP violating MSSM. In a given channel we show that the cross-section for all i (=1,2,3) can be above 0.1 fb provided $M_{H_{2,3}}\la 300$ GeV. This should be detectable at a Next Linear Collider and would provide evidence for scalar-pseudoscalar mixing.

hep-ph↗
arXiv2001

Direct CP Asymmetry of B -> X_d γin the effective SUSY model

We investigate the effect of supersymmetric CP violating phases on the inclusive decay B\to X_dγ. Although such a decay contains a large background from B\to X_sγ, if isolated it may exhibit sizeable CP violation, both in the Standard Model (SM) and in the context of models beyond the SM. With unconstrained supersymmetric CP violating phases we show that the direct CP asymmetry (A_CP) lies in the region -40% \le A_CP \le 40%, where a positive asymmetry would constitute a clear signal of physics beyond the SM. Even if a direct measurement of B\to X_dγproves too dif ficult experimentally, its asymmetry contributes non-negligibly to the measurements of A_CP for B\to X_sγ, and thus should be included in future analyses. We show t hat there may be both constructive and destructive interference between A^dγ_CP and A^sγ_CP.

hep-ph↗
arXiv2001

Radiative corrections to the decay $H^+ \to W^+ A^0$

Full one-loop electroweak corrections to the on-shell decay $H^+ \to W^+A^0$ are computed in the framework of models with two Higgs doublets (THDM). Such a decay may be dominant for $H^{\pm}$ over a wide range of parameter space relevant at present and future colliders. We show that the corrections may approach 40% and in particular are sensitive to $λ_5$, which parametrizes the discrete symmetry breaking term. We suggest that a measurement of the branching ratio of $H^+ \to W^+A^0$ may offer a possibility of measuring the magnitude of $λ_5$.

hep-ph↗
arXiv2001

Effect of Supersymmetric phases on the Direct CP Asymmetry of B -> X_d γ

We investigate the effect of supersymmetric CP violating phases on the inclusive decay B\to X_dγ. Although such a decay contains a large background from B\to X_sγ, if isolated it may exhibit sizeable CP violation, both in the Standard Model (SM) and in the context of models beyond the SM. With unconstrained supersymmetric CP violating phases we show that the direct CP asymmetry (A_CP) lies in the region -40% \le A_CP \le 40%, where a positive asymmetry would constitute a clear signal of physics beyond the SM. Even if a direct measurement of B\to X_dγproves too dif ficult experimentally, its asymmetry contributes non-negligibly to the measurements of A_CP for B\to X_sγ, and thus should be included in future analyses. We show t hat there may be both constructive and destructive interference between A^dγ_CP and A^sγ_CP.

hep-ph↗
arXiv2000

Single Charged Higgs production as a probe of CP violation at a Muon Collider

We consider single charged Higgs ($H^{\pm}$) production in association with a $W^{\pm}$ boson at $μ^+μ^-$ colliders, in the context of the general CP violating Two Higgs Doublet Model (2HDM). We find that large cross-sections for the processes $μ^+μ^-\to H^+W^-,H^-W^+$ are possible, and offer an attractive way of producing $H^{\pm}$ at $μ^+μ^-$ colliders. The difference in the cross-sections for $H^+W^-$ and $H^-W^+$ may exceed 1000 fb, and this represents a novel way of probing CP violation in the Higgs sector.

hep-ph↗
arXiv1999

Charged and Pseudoscalar Higgs production at a Muon Collider

We consider single charged Higgs ($H^{\pm}$) and pseudoscalar Higgs ($A^0$) production in association with a gauge boson at $μ^+μ^-$ colliders. We find that the tree-level t-channel and s-channel contributions to $μ^+μ^-\to H^{\pm}W^{\mp}, A^0Z$ are enhanced for large values of $\tanβ$, allowing sizeable cross-sections whose analogies at $e^+e^-$ colliders would be very small. These processes provide attractive new ways of producing such particles at $μ^+μ^-$ colliders and are superior to the conventional methods in regions of parameter space.

hep-ph↗
arXiv1998

Cascade decays of triplet Higgs bosons at LEP2

We study the Georgi-Machacek two triplet, one doublet model in the context of LEP2, and show that cascade decays of Higgs bosons to lighter Higgs bosons and a virtual vector boson may play a major role. Such decays would allow the Higgs bosons of this model to escape current searches, and in particular are of great importance for the members of the five-plet which will always decay to the three-plet giving rise to cascade signatures.

hep-ph↗
arXiv1998

Three-body decays of Higgs bosons at LEP2 and application to a hidden fermiophobic Higgs

We study the decays of Higgs bosons to a lighter Higgs boson and a virtual gauge boson in the context of the non-supersymmetric Two-Higgs-Doublet-Model (2HDM). We consider the phenomenological impact at LEP2 and find that such decays, when open, may be dominant in regions of parameter space and thus affect current Higgs boson search techniques. Three-body decays would be a way of producing light neutral Higgs bosons which have so far escaped detection at LEP due to suppressed couplings to the $Z$, and are of particular importance in the 2HDM (Model I) which allows both a light fermiophobic Higgs and a light charged scalar.

hep-ph↗
arXiv1998

Tau Lepton Mixing with Charginos and its Effects on Chargino Searches at e+e- Colliders

In bilinear R-Parity violating models where a term ε_3L_3H_2 is introduced in the superpotential, the tau lepton can mix with charginos. We show that this mixing is fully compatible with LEP1 precision measurements of the Zττand Wτν_τcouplings even for large values of ε_3 and of the induced vacuum expectation value v_3 of the tau-sneutrino. The single production of charginos at e+e- colliders is possible in this case and we present numerical values of the cross-section at LEP1, LEP2 and an NLC. We find maximum values of 10 pb at LEP1 and 1 fb at NLC, while the corresponding values at LEP2 are too small to observe.

hep-ph↗
arXiv1998

Fermiophobic and other non-minimal neutral Higgs bosons at the LHC

The phenomenology of neutral Higgs bosons from non--SUSY, extended Higgs sectors is studied in the context of the LHC, with particular attention given to the case of a fermiophobic Higgs. It is found that enhanced branching ratios to $γγ$ and $τ^+τ^-$ are possible and can provide clear signatures, while detection of a fermiophobic Higgs will be problematic beyond a mass of 130 GeV.

hep-ph↗
arXiv1996

Non-minimal neutral Higgs bosons at LEP2

We study the phenomenology of the neutral Higgs sector of a non-SUSY non-minimal Standard Model. Models with more than one Higgs doublet are possible, and may contain neutral Higgs scalars with branching ratios significantly different to those of the Minimal Standard Model Higgs boson. We show how these differences may be exploited at LEP2 in order to distinguish the non-minimal Standard Model from the minimal version.

hep-ph↗
arXiv1995

Fermiophobic Higgs bosons at the Tevatron

Higgs bosons with negligible couplings to fermions can arise in various non--minimal Higgs sectors. We show that such a particle could be discovered during the current run at the Tevatron, and would be evidence against a minimal supersymmetric Higgs sector.

hep-ph↗
arXiv1995

Hidden top quark decays to charged Higgs scalars at the Tevatron

Charged Higgs scalars light enough to contribute to top quark decays are possible in various non--minimal Higgs models. We show that such a decay would be consistent with the current Tevatron data, and will remain hidden until a larger luminosity can be achieved.

hep-ph↗