REVIEW
Nonleptonic weak decays of charmed mesons
High Energy Physics - Phenomenology · Submitted 14 Nov 1994 · 25 references
Pith's verdict: A careful, self-aware update of a long-running charm-decay fit; the new piece is modest but real, and the reader's headline complaint about the chi-squared does not survive contact with the text.
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Referee report
The paper
The paper claims
Two-body charmed-meson decays only come out right when W-exchange, annihilation, and rescattering through nearby resonances are added to the factorized weak Hamiltonian.
The reading
What carries the argument
The load-bearing device is the rescattering replacement $A(D → V_h P_k) = A_w(D → V_h P_k) + c_{hk}[e^{iδ_8} - 1] Σ_{h'k'} c_{h'k'} A_w(D → V_{h'}P_{k'})$, where the $c_{hk}$ are normalized couplings of the resonance to the two-body channel and $sin δ_8 e^{iδ_8} = Γ_R / (2(M_R - M_D) - iΓ_R)$ fixes the strong phase from the resonance mass and width. This is what turns a set of real factorized amplitudes into amplitudes with large relative strong phases, and it is what produces the SU(3) violations, since the $K$ and $π$ resonances sit at different masses and therefore give different phases in different isospin channels. For the Cabibbo-forbidden $D^0$ channels the same logic requires isoscalar scalar resonances; the authors compress their freedom to three parameters by analogy with the tensor mesons $f_2(1270)$ and $f'_2(1525)$, imposing $a = 1/(√2 tan φ)$ so that the lighter isoscalar does not decay to $ππ$.
Extended reading notes
Core claim
The central claim is that a factorized weak amplitude is the wrong starting point unless it is immediately dressed by two effects the authors treat as physics rather than as corrections: W-exchange/annihilation matrix elements, written via current divergences and parametrized by two numbers $W_{PP}$ and $W_{PV}$ that turn out considerably larger than naive pole estimates, and final-state interactions modelled as rescattering through the nearest $0^-$ and $0^+$ resonances. With these, the authors refit the Cabibbo-allowed $D^0$ and $D^+$ rates, the Cabibbo-allowed and first-forbidden $D^+$ and $D_s^+$ rates, and extend the analysis to the Cabibbo-forbidden $D^0$ channels, adding only three parameters for the unmeasured isoscalar scalars. The fit reproduces the observed SU(3) violations: the $K^+K^-$-to-$π^+π^-$ ratio far above the symmetric prediction, a non-zero $D^0 → K^0 K^0$ rate that vanishes in factorization, and the ratio $R_+ ≃ 3.55$ in the exotic $D^+$ channels, which arises here from several small SU(3)-breaking effects adding coherently. The authors also note where the model strains: the predicted $R'_+ = B.R.(D^+ → φK^+)/B.R.(D^+ → φπ^+)$ is much smaller than the quoted measurement, which itself is only 2.5 standard deviations from zero.
Load-bearing premise
The strong phases that make the whole scheme work are generated by resonances whose masses, widths, and couplings are either unmeasured or themselves fitted, so the agreement with data rests on objects the paper has to postulate.
Editorial extensions
If this is right
- The $K^+K^-$ to $π^+π^-$ ratio and the non-zero $D^0 → K^0K^0$ rate are consequences of rescattering phases rather than of short-distance SU(3) breaking, so any model that gets them from quark-mass or decay-constant differences alone is aiming at the wrong mechanism.
- The large value $R_+ ≃ 3.55$ of $D^+ → π^+π^0$ relative to $D^+ → K_S π^+$ follows from several small SU(3)-breaking effects contributing with the same sign.
- CP-violating asymmetries of order $10^{-3}$ are expected in Cabibbo-forbidden $D$ channels, with the strong phases supplied by the same resonance model used for the rates.
- The doubly Cabibbo-suppressed ratio $R_{Kπ}^0$ is predicted at $0.89 × 10^{-2}$, about 3.4 times the SU(3) expectation of $tan^4θ_C$, driven mainly by W-exchange contributions of opposite sign in the two amplitudes.
Reading between the lines
- If the scalar isoscalar states invoked here are later found near the fitted masses of about 1778 and 2148 MeV with roughly the fitted widths, the same resonance-rescattering bookkeeping becomes a template for $B$ decays, where strong phases are otherwise almost unconstrained.
- The three-parameter compression rests on an analogy with the tensor mesons rather than on data; measuring the $f_0 → K\bar K$ versus $f'_0 → ππ$ branching pattern would either fix the mixing angle independently or break the analogy outright.
- Because every predicted asymmetry traces back to fitted strong phases, a measured asymmetry at the $10^{-3}$ level would not by itself confirm this particular phase assignment; the rates and the asymmetries would have to be checked jointly.
Original abstract
A previous analysis of two-body Cabibbo allowed nonleptonic decays of $D^0$ mesons and of Cabibbo allowed and first-forbidden decays of $D^+$ and $D_s^+$ has been adjourned using more recent experimental data and extended to the Cabibbo forbidden decays of $D^0$. Annihilation and W-exchange contributions as well as final state interaction effects (assumed to be dominated by nearby resonances) have been included and are in fact crucial to obtain a reasonable agreement with the experimental data, which show large flavour SU(3) violations. New fitting parameters are necessary to describe rescattering effects for Cabibbo forbidden $D^0$ decays, given the lack of experimental informations on isoscalar resonances. We keep their number to a minimum - three - using phenomenologically based considerations. We also discuss CP violating asymmetries.
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
A previous analysis of two-body Cabibbo allowed nonleptonic decays of $D^0$ mesons and of Cabibbo allowed and first-forbidden decays of $D^+$ and $D_s^+$ has been adjourned using more recent experimental data and extended to the Cabibbo forbidden decays of $D^0$. Annihilation and W-exchange contributions as well as final state interaction effects (assumed to be dominated by nearby resonances) have been included and are in fact crucial to obtain a reasonable agreement with the experimental data, which show large flavour SU(3) violations. New fitting parameters are necessary to describe rescattering effects for Cabibbo forbidden $D^0$ decays, given the lack of experimental informations on isoscalar resonances. We keep their number to a minimum - three - using phenomenologically based considerations. We also discuss CP violating asymmetries.
background contribution method result interpretation main claim
| # | sentence | role | the authors' own work | states the main conclusion | strength |
|---|---|---|---|---|---|
| s0 | A previous analysis of two-body Cabibbo allowed nonleptonic decays of $D^0$ mesons and of Cabibbo allowed and first-forbidden decays of $D^+$ and $D_s^+$ has been adjourned using more recent experimental data and extended to the Cabibbo forbidden decays of $D^0$. | contribution 0.86 | 0.65 | 0.10 | asserted 1.00 |
| s1 | Annihilation and W-exchange contributions as well as final state interaction effects (assumed to be dominated by nearby resonances) have been included and are in fact crucial to obtain a reasonable agreement with the experimental data, which show large flavour SU(3) violations. | method 0.53 | 0.69 | 0.36 | asserted 1.00 |
| s2 | New fitting parameters are necessary to describe rescattering effects for Cabibbo forbidden $D^0$ decays, given the lack of experimental informations on isoscalar resonances. | method 0.59 | 0.62 | 0.09 | asserted 0.99 |
| s3 | We keep their number to a minimum - three - using phenomenologically based considerations. | method 0.95 | 0.88 | 0.06 | asserted 0.97 |
| s4 | We also discuss CP violating asymmetries. | contribution 0.99 | 0.81 | 0.06 | asserted 0.61 |
What was examined, and what was not
- arXiv listing abstract v1
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- relations to other papers
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References
How the literature uses it
36 arXiv papers cite this in 42 sentences
Papers citing it · 29 sentences without a confident label
Uses its data or values 1 paper
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Some time ago, $ΔΓ_D$ was determined in this manner and the result $y_D ≃10^-3$ was found [ref] .
Charm Mixing - Theory · Hadron-level Analysis · 0.83
Cites it as background 12 papers
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The discovery of charm CP violation [ref] in singly-Cabibbo suppressed (SCS) two-body $D→PP$ decays, where $P$ is a pseudoscalar meson [ref] , was the result of a multi-year effort [ref] and triggered immediate theoretical interpretations [ref] .
Probing the $\Delta U=0$ Rule in Three Body Charm Decays · Introduction · 0.93
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Measurements in the charm sector have only recently achieved a sufficient level of precision to be sensitive to violation in charm transitions, which is suppressed due to the Glashow-Iliopoulos-Maiani mechanism [ref] and the small size of the Cabibbo-Kobayashi-Maskawa matrix element $|V_cb|$ [ref] .
Measurement of the CP asymmetry in $D^+ \to \pi^+ \pi^0$ decays at Belle II · Introduction · 0.81
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Small CPV was subsequently predicted in [ref] using a model for final-state interactions.
A consistent picture for large penguins in D -> pi+ pi-, K+ K- · Introduction · 0.80
Discussion
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