| 1. |
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| 2. |
- Ahmady, M R, et al.
(författare)
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ESTIMATING THE ANNIHILATION DECAY B-s -> rho gamma WITH FACTORIZATION
- 2009
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Ingår i: Modern Physics Letters A. - 0217-7323 .- 1793-6632. ; 24:39, s. 3173-3181
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Tidskriftsartikel (refereegranskat)abstract
- The branching ratio for the rare two-body B-s -> rho gamma decay is calculated using the factorization assumption. This transition is dominated by the annihilation diagrams and, in principle, prone to receiving substantial contributions from new physics. We estimate Br(B-s -> rho gamma) approximate to 1.6 x 10(-9) within the Standard Model and investigate the sensitivity of this decay mode to the effects of two new physics scenarios: vector quark model and supersymmetry. Our results indicate that the shift in branching ratio is at most around 10% with the addition of vector quarks and is negligibly small in the constrained minimal supersymmetric extension of the Standard Model.
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| 3. |
- Allanach, Benjamin C., et al.
(författare)
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Simple and statistically sound strategies for analysing physical theories
- 2022
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Ingår i: Reports on progress in physics (Print). - : Institute of Physics Publishing (IOPP). - 0034-4885 .- 1361-6633. ; 85:5
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Forskningsöversikt (refereegranskat)abstract
- Physical theories that depend on many parameters or are tested against data from many different experiments pose unique challenges to statistical inference. Many models in particle physics, astrophysics and cosmology fall into one or both of these categories. These issues are often sidestepped with statistically unsound ad hoc methods, involving intersection of parameter intervals estimated by multiple experiments, and random or grid sampling of model parameters. Whilst these methods are easy to apply, they exhibit pathologies even in low-dimensional parameter spaces, and quickly become problematic to use and interpret in higher dimensions. In this article we give clear guidance for going beyond these procedures, suggesting where possible simple methods for performing statistically sound inference, and recommendations of readily-available software tools and standards that can assist in doing so. Our aim is to provide any physicists lacking comprehensive statistical training with recommendations for reaching correct scientific conclusions, with only a modest increase in analysis burden. Our examples can be reproduced with the code publicly available at Zenodo.
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| 4. |
- Eriksson, David, et al.
(författare)
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Charged Higgs bosons in minimal supersymmetry : updated constraints and experimental prospects
- 2008
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Ingår i: Journal of High Energy Physics (JHEP). - : Springer Science and Business Media LLC. - 1126-6708 .- 1029-8479. ; 11:035
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Tidskriftsartikel (refereegranskat)abstract
- We discuss the phenomenology of charged Higgs bosons in the MSSM with minimal flavor violation. In addition to the constrained MSSM (CMSSM) with universal soft supersymmetry breaking mass parameters at the GUT scale, we explore non-universal Higgs mass models (NUHM) where this universality condition is relaxed. To identify the allowed parameter space regions, we apply constraints from direct searches, low energy observables, and cosmology. We find that values of the charged Higgs mass as low as mH+ 135 GeV can be accommodated in the NUHM models, but that several flavor physics observables disfavor large H+ contributions, associated with high tan β, quite independently of MSSM scenario. We confront the constrained scenarios with the discovery potentials reported by ATLAS and CMS, and find that the current exclusion by indirect constraints is similar to the expected LHC discovery reach with 30 fb−1 of data. Finally, we evaluate the sensitivity of the presented discovery potential to the choice of MSSM benchmark scenario. This sensitivity is found to be higher in the case of a light (mH+ < mt) charged Higgs.
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| 5. |
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| 6. |
- Mahmoudi, Farvah, et al.
(författare)
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Flavor constraints on two-Higgs-doublet models with general diagonal Yukawa couplings
- 2010
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Ingår i: Physical Review D - Particles, Fields, Gravitation and Cosmology. - 1550-7998. ; 81:3, s. 035016-
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Tidskriftsartikel (refereegranskat)abstract
- We consider constraints from flavor physics on two-Higgs-doublet models (2HDM) with general, flavor-diagonal, Yukawa couplings. Analyzing the charged Higgs contribution to different observables, we find that $b\to s\gamma$ transitions and $\Delta M_{B_d}$ restrict the coupling $\lambda_{tt}$ of the top quark (corresponding to $\cot\beta$ in models with a $Z_2$ symmetry) to $|\lambda_{tt}|<1$ for $m_{H^+}\lesssim 500$ GeV. Stringent constraints from $B$ meson decays are obtained also on the other third generation couplings $\lambda_{bb}$ and $\lambda_{\tau\tau}$, but with stronger dependence on $m_{H^+}$. For the second generation, we obtain constraints on combinations of $\lambda_{ss}$, $\lambda_{cc}$, and $\lambda_{\mu\mu}$ from leptonic $K$ and $D_s$ decays.The limits on the general couplings are translated to the common 2HDM types I -- IV with a $Z_2$ symmetry, and presented on the $(m_{H^+},\tan\beta)$ plane. The flavor constraints are most excluding in the type II model which lacks a decoupling limit in $\tan\beta$. We obtain a lower limit $m_{H^+}\gtrsim 300$ GeV in models of type II and III, while no lower bound on $m_{H^+}$ is found for types I and IV.
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| 7. |
- Mahmoudi, Farvah
(författare)
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New constraints on supersymmetric models from b --> s gamma
- 2007
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Ingår i: Journal of High Energy Physics (JHEP). - : Springer Science and Business Media LLC. - 1126-6708 .- 1029-8479. ; 12, s. 026-
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Tidskriftsartikel (populärvet., debatt m.m.)abstract
- We provide an analysis of the parameter space of several supersymmetry breaking scenarios such as the minimal supergravity (mSUGRA) model and the non universal Higgs mass (NUHM) framework, as well as the Anomaly Mediated Supersymmetry Breaking (AMSB) and the Gauge Mediated Supersymmetry Breaking (GMSB) models, in the light of a novel observable in b → sγ transitions, i.e. the isospin symmetry breaking in the exclusive B → K*γ decays. We find that in many cases, this observable provides severe restrictions on the allowed parameter space regions for the mentioned models. Moreover, we provide a few examples of investigations of the physical masses of supersymmetric particles and search for the excluded values. The constraints from the branching ratio associated to b → sγ are also presented here for all the examined parameter space regions. A comparison with Bs → μ+μ− branching ratio has also been performed.
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| 8. |
- Mahmoudi, Farvah
(författare)
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SuperIso : A Program for calculating the isospin asymmetry of B ---> K* gamma in the MSSM
- 2008
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Ingår i: Computer Physics Communications. - : Elsevier BV. - 0010-4655 .- 1879-2944. ; 178:10, s. 745-754
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Tidskriftsartikel (populärvet., debatt m.m.)abstract
- We present a program for calculating the isospin symmetry breaking in B -> , K*gamma decays in the MSSM with minimal flavor violation. This program calculates the NLO supersymmetric contributions to the isospin asymmetry, using the effective Hamiltonian approach and within the QCD factorization method. We show that isospin symmetry breaking proves to be a very restrictive observable, in particular in the mSUGRA parameter space. The program also calculates the inclusive branching ratio associated to b -> , s gamma transition, as a comparison reference.
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| 9. |
- Mahmoudi, Farvah
(författare)
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SuperIso v2.3 : A program for calculating flavor physics observables in supersymmetry
- 2009
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Ingår i: Computer Physics Communications. - : Elsevier BV. - 0010-4655 .- 1879-2944. ; 180:9, s. 1579-1613
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Tidskriftsartikel (refereegranskat)abstract
- We describe SuperIso v2.3 which is a public program for evaluation of flavor physics observables in the minimal supersymmetric extension of the Standard Model (MSSM). SuperIso v2.3, in addition to the isospin asymmetry of B→K∗γ, which was the main purpose of the first version, incorporates new flavor observables such as the branching ratio of Bs→μ+μ−, the branching ratio of B→τντ, the branching ratio of B→Dτντ and the branching ratio of K→μνμ. The calculation of the branching ratio of B→Xsγ is also improved in this version, as it now includes NNLO Standard Model contributions in addition to partial NLO supersymmetric contributions. The program also computes the muon anomalous magnetic moment (g−2). Four sample models are included in the package, namely mSUGRA, NUHM, AMSB and GMSB. SuperIso uses a SUSY Les Houches Accord file (SLHA1 or SLHA2) as input, which can be either generated automatically by the program via a call to external spectrum calculators, or provided by the user. The calculation of the observables is detailed in the Appendices, where a suggestion for the allowed intervals for each observable is also provided.
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| 10. |
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