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An improved observable for the forward-backward asymmetry in B -> K* l+ l- and Bs -> phi l+ l-
High Energy Physics - Phenomenology · Submitted 22 Jul 2010
abstract compiled · 2026-09-23 · no language-model review
The authors' main claim We study the decay B -> K* l+ l- in the QCD factorization approach and propose a new integrated observable whose dependence on the form factors is almost negligible, consequently the non--perturbative error is significantly reduced and indeed its overall theoretical error is dominated by perturbative scale uncertainties.
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The abstract, sentence by sentence
We study the decay B -> K* l+ l- in the QCD factorization approach and propose a new integrated observable whose dependence on the form factors is almost negligible, consequently the non--perturbative error is significantly reduced and indeed its overall theoretical error is dominated by perturbative scale uncertainties. The new observable we propose is the ratio between the integrated forward--backward asymmetry in the [4,6] GeV^2 and [1,4] GeV^2 dilepton invariant mass bins. This new observable is particularly interesting because, when compared to the location of the zero of the FBA spectrum, it is experimentally easier to measure and its theoretical uncertainties are almost as small; moreover it displays a very strong dependence on the phase of the Wilson coefficient C_10 that is otherwise only accessible through complicated CP violating asymmetries. We illustrate the new physics sensitivity of this observable within the context of few extensions of the Standard Model, namely the SM with four generations, an MSSM with non--vanishing source of flavor changing neutral currents in the down squark sector and a Z' model with tree level flavor changing couplings.
background contribution method result interpretation main claim
| # | sentence | role | the authors' own work | states the main conclusion | strength |
|---|---|---|---|---|---|
| s0 | We study the decay B -> K* l+ l- in the QCD factorization approach and propose a new integrated observable whose dependence on the form factors is almost negligible, consequently the non--perturbative error is significantly reduced and indeed its overall theoretical error is dominated by perturbative scale uncertainties. | contribution 0.98 | 0.93 | 0.64 | asserted 1.00 |
| s1 | The new observable we propose is the ratio between the integrated forward--backward asymmetry in the [4,6] GeV^2 and [1,4] GeV^2 dilepton invariant mass bins. | contribution 0.91 | 0.88 | 0.15 | asserted 1.00 |
| s2 | This new observable is particularly interesting because, when compared to the location of the zero of the FBA spectrum, it is experimentally easier to measure and its theoretical uncertainties are almost as small; moreover it displays a very strong dependence on the phase of the Wilson coefficient C_10 that is otherwise only accessible through complicated CP violating asymmetries. | interpretation 0.93 | 0.62 | 0.25 | asserted 1.00 |
| s3 | We illustrate the new physics sensitivity of this observable within the context of few extensions of the Standard Model, namely the SM with four generations, an MSSM with non--vanishing source of flavor changing neutral currents in the down squark sector and a Z' model with tree level flavor changing couplings. | contribution 0.74 | 0.79 | 0.09 | asserted 1.00 |
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The paper
Original abstract
We study the decay B -> K* l+ l- in the QCD factorization approach and propose a new integrated observable whose dependence on the form factors is almost negligible, consequently the non--perturbative error is significantly reduced and indeed its overall theoretical error is dominated by perturbative scale uncertainties. The new observable we propose is the ratio between the integrated forward--backward asymmetry in the [4,6] GeV^2 and [1,4] GeV^2 dilepton invariant mass bins. This new observable is particularly interesting because, when compared to the location of the zero of the FBA spectrum, it is experimentally easier to measure and its theoretical uncertainties are almost as small; moreover it displays a very strong dependence on the phase of the Wilson coefficient C_10 that is otherwise only accessible through complicated CP violating asymmetries. We illustrate the new physics sensitivity of this observable within the context of few extensions of the Standard Model, namely the SM with four generations, an MSSM with non--vanishing source of flavor changing neutral currents in the down squark sector and a Z' model with tree level flavor changing couplings.
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References
How the literature uses it
11 arXiv papers cite this in 11 sentences
Papers citing it · 6 sentences without a confident label
Cites it as background 5 papers
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While the phenomenology of the low $q^2$ region has received lots of attention in the past see e.g. [ref] [ref] [ref] [ref] [ref] [ref] [ref] [ref] [ref] [ref] , the theoretical activities at low recoil are rather recent.
B -> K(*) l+ l- @ Low Recoil and Physics Implications · Introduction · 0.98
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The analyses of these decays in the context of the SM as well as in some NP models have been performed in the literature: $$ [ref] , $$ [ref] , $$ [ref] , $$ [ref] , $$ [ref] .
New Physics in b -> s mu+ mu-: CP-Conserving Observables · Introduction · 0.97
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The opposite kinematical region of large recoil has been subjected to the question of optimized observables as well, e.g., [ref] .
General Analysis of B -> K^(*) l^+ l^- Decays at Low Recoil · Introduction · 0.96
What it cites · 19 sentences without a confident label
Uses the method or tool of 1 paper
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where $s_W$ is the weak mixing angle and, following Ref. [ref] , we defined[In Ref. [ref] the rescaling of the $B$ couplings is performed but the hat symbol is not explicitly introduced.] $B̂_bs^L ≡B_bs^L (g_2 m_Z/g_1 m_Z^')$.
$b \to s$ Transitions in Family-dependent $U(1)^\prime$ Models · Family–dependent $U(1)^'$ · 0.87
Uses data or values from 8 papers
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From the analyses in Refs. [ref] we extract ranges for these two parameters that are phenomenologically viable; in the numerical analysis we take $m_t^' = 500$ and $|λ_tt^'^s|<0.1$.
SM with four generations: Selected implications for rare B and K decays · 4th generation · 0.99
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From the analyses in Refs. [ref] we extract ranges for these two parameters that are phenomenologically viable; in the numerical analysis we take $m_t^' = 500$ and $|λ_tt^'^s|<0.1$.
Patterns of Flavour Violation in the Presence of a Fourth Generation of Quarks and Leptons · 4th generation · 0.99
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The inclusive $BR(B →X_s ℓ^+ ℓ^-) = (1.60 ±0.51) ×10^-6$ is measured [ref] and is consistent with the NNLO prediction of the Standard Model (SM), $(1.62 ±0.14)×10^-6$ with an accuracy of around 9% [ref] ; given the large experimental uncertainty, this measurement allows for new physics contributions at the $∼30%$ level.
Logarithmically Enhanced Corrections to the Decay Rate and Forward Backward Asymmetry in anti-B --> X(s) l+ l- · Introduction · 0.90
Cites as background 17 papers
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The importance of the flavor-changing semileptonic decays, $b →s(d) l^+ l^-$ for searching effects of new physics has been recognized for a very long time [ref] .The process is especially important because its amplitude is very sensitive to the presence of heavy virtual quarks, scaling as $(mass_quark)^2$.
New physics reach of the decay mode $\bar{B} \to \bar{K}^{*0}\ell^+\ell^-$ · Introduction · 0.93
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The importance of the flavor-changing semileptonic decays, $b →s(d) l^+ l^-$ for searching effects of new physics has been recognized for a very long time [ref] .The process is especially important because its amplitude is very sensitive to the presence of heavy virtual quarks, scaling as $(mass_quark)^2$.
Radiative and Electroweak Penguin Decays of B Mesons · Introduction · 0.93
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The importance of the flavor-changing semileptonic decays, $b →s(d) l^+ l^-$ for searching effects of new physics has been recognized for a very long time [ref] .The process is especially important because its amplitude is very sensitive to the presence of heavy virtual quarks, scaling as $(mass_quark)^2$.
New Physics at a Super Flavor Factory · Introduction · 0.93
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