REVIEW
The rare decays B --> K(*) anti-K(*) and R-parity violating supersymmetry
High Energy Physics - Phenomenology · Submitted 12 Mar 2006 · 30 references
Pith's verdict: Useful RPV bounds and interesting CP predictions, but the advertised fL conclusion is not supported because VV annihilation amplitudes are dropped.
T0 · AI review
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Referee report
The paper
The paper claims
This paper claims that R-parity-violating supersymmetry can strongly alter the rates and CP asymmetries of rare B-to-K-anti-K decays while barely moving the K* anti-K* polarizations, and it derives new coupling bounds from current data.
The reading
What carries the argument
The machinery is QCD factorization for the hadronic matrix elements supplemented by a set of tree-level four-fermion operators from an R-parity-violating superpotential. The paper writes the total amplitude as $A = A_{\rm SM}^f + A_{\rm SM}^a + A_{\not R_p}$, where the RPV part is built from five complex product couplings $\lambda''_{i23}\lambda''^*_{i12}$, $\lambda'_{i13}\lambda'^*_{i22}$, $\lambda'_{i22}\lambda'^*_{i31}$, $\lambda'_{i12}\lambda'^*_{i32}$, and $\lambda'_{i23}\lambda'^*_{i21}$, each carrying a weak phase $\phi_{\not R_p}$; these couplings enter through $1/m_{\tilde f}^2$ propagator factors with QCD running factors, and are convoluted with the same form factors, decay constants, and next-to-leading-order coefficients $a_i$ and $b_i$ as the SM amplitude. This lets one scan the coupling magnitudes and phases against the measured branching ratios and the one measured CP asymmetry, producing the allowed regions and the predictions.
Extended reading notes
Core claim
The central claim is that the R-parity-violating part of the amplitude, built from tree-level sfermion exchange with complex couplings $\lambda''\lambda''^*$ or $\lambda'\lambda'^*$, can interfere with the SM penguin amplitude strongly enough to change the branching ratios and direct CP asymmetries of $B\to K^{(*)}\bar K^{(*)}$ by large factors, while barely touching the longitudinal polarization of the two vector modes. Concretely, with one 100 GeV sfermion at a time, the fits give $|\lambda''_{i23}\lambda''^*_{i12}| \le 2.9\times10^{-3}$ and $|\lambda'_{i13}\lambda'^*_{i22}| \le 2.2\times10^{-3}$, with the latter two $\lambda'$ products tighter than previously published limits. Using these constrained ranges, the unmeasured branching ratios are predicted to span roughly $5\times10^{-9}$ to $2\times10^{-5}$, direct CP asymmetries may reach $\pm 0.99$ in some modes, and $f_L(B\to K^{*+}\bar K^{*0}, K^{*0}\bar K^{*0})$ stays between 0.59 and 0.97. The paper states this as a testable separation: RPV can make the rates and asymmetries look very non-standard, yet the $K^*\bar K^*$ channels still look longitudinally polarized.
Load-bearing premise
The load-bearing premise is that one sfermion with mass 100 GeV contributes at a time, so each of the five RPV coupling products is constrained independently; if multiple sfermion exchanges interfere, the upper limits and the predicted ranges in Table III no longer follow directly from the data.
Editorial extensions
If this is right
- Unmeasured modes get concrete target windows: for example, $B(B\to K^{*+}\bar K^{*0})$ is predicted below about $2\times10^{-5}$, below the current upper limit, so a future measurement inside that window would be consistent with these RPV couplings.
- Direct CP asymmetries in several modes can be far larger than the SM's small values; for $B^0_d\to K^{*0}\bar K^0$ the allowed range reaches $\pm 0.99$, so a large observed asymmetry in these pure-penguin decays would point to new CP-violating phases of the RPV type.
- The longitudinal polarization fractions $f_L$ for $B\to K^*\bar K^*$ remain in roughly 0.59--0.97 under all five couplings, so a measured suppression of $f_L$ would disfavor this simple one-coupling-at-a-time RPV explanation.
- The bounds scale as $(m_{\tilde f}/100\,\mathrm{GeV})^2$, so the same constraints translate immediately to heavier sfermions by weakening the limits quadratically.
- Improved measurements of the already-seen modes, such as $B^+\to K^+\bar K^0$ and its CP asymmetry, will directly shrink the currently allowed coupling bands.
Reading between the lines
- The one-sfermion-at-a-time assumption means the bounds are per-product rather than global; a combined fit allowing several sfermions to interfere could either loosen or tighten the limits, and would be the natural next step.
- Because the same five products also feed other $b\to d s\bar s$ observables, such as $\phi\pi^0$ modes and $B_s$ decays, a global fit across channels could sharpen the discrimination.
- The near-independence of $f_L$ is itself a diagnostic: models that explain polarization puzzles generally need right-handed currents or new tensor operators, whereas RPV here changes rates and CP asymmetries while leaving the helicity structure nearly SM-like, so a future experiment seeing both large CP violation and SM-like $f_L$ would point toward scalar-exchange new physics.
Original abstract
We study the branching ratios, the direct CP asymmetries in $B\to K^{(*)}\bar{K}^{(*)}$ decays and the polarization fractions of $B\to K^{*}\bar{K}^{*}$ decays by employing the QCD factorization in the minimal supersymmetric standard model with R-parity violation. We derive the new upper bounds on the relevant R-parity violating couplings from the latest experimental data of $B\to K^{(*)}\bar{K}^{(*)}$, and some of these constraints are stronger than the existing bounds. Using the constrained parameter spaces, we predict the R-parity violating effects on the other quantities in $B\to K^{(*)}\bar{K}^{(*)}$ decays which have not been measured yet. We find that the R-parity violating effects on the branching ratios and the direct $CP$ asymmetries could be large, nevertheless their effects on the longitudinal polarizations of $B\to K^{*}\bar{K}^{*}$ decays are small. Near future experiments can test these predictions and shrink the parameter spaces.
The compiled record
The paper's own sentences, arranged, kept beside the review and separate from it. Each label is drawn from a closed vocabulary; the number beside it is the probability the classifier gave that label. Numbers in the tables are the authors', checked by code. No sentence in this record was written by a model.
The abstract, sentence by sentence
We study the branching ratios, the direct CP asymmetries in $B\to K^{(*)}\bar{K}^{(*)}$ decays and the polarization fractions of $B\to K^{*}\bar{K}^{*}$ decays by employing the QCD factorization in the minimal supersymmetric standard model with R-parity violation. We derive the new upper bounds on the relevant R-parity violating couplings from the latest experimental data of $B\to K^{(*)}\bar{K}^{(*)}$, and some of these constraints are stronger than the existing bounds. Using the constrained parameter spaces, we predict the R-parity violating effects on the other quantities in $B\to K^{(*)}\bar{K}^{(*)}$ decays which have not been measured yet. We find that the R-parity violating effects on the branching ratios and the direct $CP$ asymmetries could be large, nevertheless their effects on the longitudinal polarizations of $B\to K^{*}\bar{K}^{*}$ decays are small. Near future experiments can test these predictions and shrink the parameter spaces.
background contribution method result interpretation main claim
| # | sentence | role | the authors' own work | states the main conclusion | strength |
|---|---|---|---|---|---|
| s0 | We study the branching ratios, the direct CP asymmetries in $B\to K^{(*)}\bar{K}^{(*)}$ decays and the polarization fractions of $B\to K^{*}\bar{K}^{*}$ decays by employing the QCD factorization in the minimal supersymmetric standard model with R-parity violation. | contribution 0.93 | 0.94 | 0.06 | asserted 0.94 |
| s1 | We derive the new upper bounds on the relevant R-parity violating couplings from the latest experimental data of $B\to K^{(*)}\bar{K}^{(*)}$, and some of these constraints are stronger than the existing bounds. | result 0.92 | 0.95 | 0.29 | asserted 1.00 |
| s2 | Using the constrained parameter spaces, we predict the R-parity violating effects on the other quantities in $B\to K^{(*)}\bar{K}^{(*)}$ decays which have not been measured yet. | contribution 0.78 | 0.92 | 0.10 | asserted 0.99 |
| s3 | We find that the R-parity violating effects on the branching ratios and the direct $CP$ asymmetries could be large, nevertheless their effects on the longitudinal polarizations of $B\to K^{*}\bar{K}^{*}$ decays are small. | result 1.00 | 0.95 | 0.63 | hedged possibility 0.81 |
| s4 | Near future experiments can test these predictions and shrink the parameter spaces. | future work 0.98 | 0.13 | 0.09 | hedged possibility 0.85 |
What was examined, and what was not
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Figures
Figures reproduced from arXiv:hep-ph/0603088 by the authors.
References
How the literature uses it
1 arXiv paper cite this in 1 sentence
Discussion
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