Flavor Catalog v0.4
102 entries
Catalog · Secondary · B013

B013 $B_s^0\to\phi(1020)\gamma$

Exclusive radiative $B_s$ decay via b $ \to $ s $\gamma$
Status REVIEWED VERIFIED High Code: NO Priority Low

PDG / equivalent values

Observable Value Year Experiment / source Provenance
$B(B_s0 \to \phi(1020$) $\gamma$) (3.4 +/- 0.4) x 10^-5 2025 PDG B_s0 listing, 2025 update source ↑
$B(B_s0 \to \phi(1020$) $\gamma$) (34.0 +/- 3.2) x 10^-6 2024 HFLAV rare decays, end-of-year 2024 source ↑
$S_\phi \gamma$ in $B_s0 \to \phi \gamma$ 0.43 +/- 0.30(stat) +/- 0.11(syst) 2019 LHCb arXiv:1905.06284; also listed in PDG 2025 source ↑
$C_\phi \gamma$ in $B_s0 \to \phi \gamma$ 0.11 +/- 0.29(stat) +/- 0.11(syst) 2019 LHCb arXiv:1905.06284; also listed in PDG 2025 source ↑
$A_\Delta_\phi \gamma$ in $B_s0 \to \phi \gamma$ -0.67 +0.37 -0.41(stat) +/- 0.17(syst) 2019 LHCb arXiv:1905.06284; also listed in PDG 2025 source ↑
$B(B_s0 \to \phi \gamma$), Belle $\Upsilon(5S$) input (3.6 +/- 0.5(stat) +/- 0.3(syst) +/- 0.6(f_s)) x 10^-5 2014 Belle arXiv:1411.7771 source ↑
overall tensor contribution $F_{f2}$ in $B_s0 \to $ K+K- $\gamma$ 16.8 +/- 0.5(stat) +/- 0.7(syst)% 2024 LHCb arXiv:2406.00235 source ↑
$B(B_s0 \to $ f2'(1525) $\gamma$) / $B(B_s0 \to \phi \gamma$), preferred solution 19.4 +0.9 -0.8(stat) +1.4 -0.5(syst) +/- 0.5(B)% 2024 LHCb arXiv:2406.00235 source ↑
$A_T^(2$) in $B_s0 \to \phi$ e+e-, very-low-q2 photon-polarisation proxy -0.045 +/- 0.235(stat) +/- 0.014(syst) 2024 LHCb arXiv:2411.10219 source ↑
$A_T^{ImCP}$ in $B_s0 \to \phi$ e+e-, very-low-q2 photon-polarisation proxy 0.002 +/- 0.247(stat) +/- 0.016(syst) 2024 LHCb arXiv:2411.10219 source ↑
longitudinal polarisation fraction $F_L(\phi$) in $B_s0 \to \phi$ e+e- < 11.5% at 90% CL
90% CL (upper limit)
 2024 LHCb arXiv:2411.10219 source ↑

Why this constrains the RS scan

This this catalog wave entry is SECONDARY under flavor\_catalog/PRIORITY\_TIERS.md. The physics motivation is direct: \(B_s^0\to\phi\gamma\) probes the electromagnetic dipole transition \(b\to s\gamma\), but with a helicity handle that the inclusive \(B\to X_s\gamma\) rate does not provide. In anarchic RS or composite-Higgs variants, KK fermions, KK gauge bosons, and the Higgs sector can generate chirality-flipped dipole coefficients \(C_7'\) and \(C_8'\). Those contributions may leave the inclusive rate close to the SM while shifting \(A^\Delta_{\phi\gamma}\) or \(S_{\phi\gamma}\), so this mode is a useful companion to B011 and B012.

What's changed since the original paper

Muheim--Xie--Zwicky, arXiv:0802.0876, set the pre-LHC formalism by showing how the \(B_s\) width difference exposes the time-dependent \(\sinh(\Delta\Gamma_s t/2)\) coefficient and therefore the right-handed photon amplitude. Belle measured \(B_s^0\to\phi\gamma\) at the \(\Upsilon(5S)\) in arXiv:1411.7771, contributing one input to the modern PDG/HFLAV branching-fraction average. LHCb's arXiv:1905.06284 analysis is the current time-dependent CP reference: it gives the first \(S_{\phi\gamma}\) and \(C_{\phi\gamma}\) measurements in a radiative \(B_s\) decay and updates the earlier untagged \(A^\Delta_{\phi\gamma}\) result. LHCb arXiv:2406.00235 added a Run-1/Run-2 amplitude analysis of \(B_s^0\to K^+K^-\gamma\), clarifying the resonant composition around the \(\phi(1020)\), while arXiv:2411.10219 uses the very-low-\(q^2\) \(B_s^0\to\phi e^+e^-\) angular distribution as a virtual photon-polarization cross-check.

Validity and model dependence

The branching fraction is experimentally established, but an exclusive constraint needs form-factor and spectator-amplitude conventions rather than only the inclusive \(C_7\) rate machinery. The time-dependent observables are cleaner chirality probes, yet their use in a scan still requires a consistent mapping from RS dipole coefficients to \(C_7,C_7'\) and \(C_8,C_8'\), the \(B_s\)-mixing phase and width-difference conventions, and an exclusive \(B_s\to\phi\) amplitude model. A catalog entry is therefore robust, while a hard likelihood is model-dependent until the dipole and exclusive-amplitude pipeline exists.

Code coverage in this repo

NO. The required greps over quarkConstraints/, qcd/, flavorConstraints/, neutrinos/, yukawa/, warpConfig/, solvers/, scanParams/, and tests/ found no implementation of \(B_s^0\to\phi\gamma\), \(S_{\phi\gamma}\), \(A^\Delta_{\phi\gamma}\), or a quark-sector \(b\to s\gamma\) dipole likelihood. The existing modern quark surface enumerates only \(\epsilon_K\), \(K\), \(B_d\), \(B_s\), and \(D^0\) neutral-meson mixing at quarkConstraints/modern/phenomenology.py:23; the \(\Delta F=2\) beauty entry points at quarkConstraints/deltaf2.py:903 and quarkConstraints/deltaf2.py:922 are mixing observables, not radiative decays. The dipole hit at flavorConstraints/muToEGamma.py:75 is the unrelated charged-lepton \(\mu\to e\gamma\) check.

Linked evidence (opens GitHub blob at flavor-catalog-website/2026q2):

Implementation difficulty

HIGH. Production use needs new \(b\to s\gamma\) dipole matching, QCD running for \(C_7,C_7'\) and \(C_8,C_8'\), exclusive \(B_s\to\phi\) form-factor and resonance inputs, and a time-dependent \(B_s\) likelihood. The current \(\Delta F=2\) code does not supply that operator basis or observable layer.

Reason: Requires new $b \to s \gamma$ dipole matching and RG, exclusive $B_s \to \phi$ form-factor/resonance inputs, and a B_s time-dependent CP/helicity likelihood; current $\Delta F = 2$ code and lepton-dipole code do not implement this observable.

Key references

Process-local keys before bibliography consolidation: PDG2025\_Bs\_phi\_gamma, HFLAV2024\_rare\_decays\_Bs\_phi\_gamma, LHCb2019\_Bs\_phi\_gamma\_CP, Belle2014\_Bs\_phi\_gamma, LHCb2024\_Bs\_KK\_gamma, LHCb2024\_Bs\_phi\_ee\_photon\_polarisation, MuheimXieZwicky2008\_Bs\_phi\_gamma, and CFW2008\_RS\_flavor.
Source SHAs
8 snapshot(s) tracked in flavor_catalog/processes/secondary/beauty/B013.yaml
Access dates
2026-05-17
Worklog
flavor_catalog/worklogs/B013/
LaTeX source
flavor_catalog/processes/secondary/beauty/B013.tex
Anchors generated
2026-05-18T01:56:20Z

branching_fraction_pdg_2025

https://pdg.lbl.gov/2025/listings/rpp2025-list-Bs-zero.pdf
accessed 2026-05-17 sha 59578d332213... snapshot B013/pdg2025_bs_phi_gamma.txt AMBIGUOUS
display (3.4 +/- 0.4) x 10^-5
AMBIGUOUS
Match 1 of 2 snapshot line 10 
L7: 
L8: Summary-table line:
L9:   Gamma_159 phi gamma, Delta B = 1 weak neutral-current mode:
L10:   (3.4 +/- 0.4) x 10^-5
L11: 
L12: Detailed listing:
L13:   Gamma(phi gamma) / Gamma_total
Match 2 of 2 snapshot line 18 
L15:   Gamma_159 / Gamma
L16:   34 +/- 4 OUR AVERAGE
L17:   DUTTA 15, Belle e+e- -> Upsilon(5S): 36 +/- 5 +/- 7
L18:   AAIJ 13, LHCb pp at 7 TeV: 33.8 +/- 3.4 +/- 2.0
L19: 
L20:   DUTTA 15 note:
L21:   Assumes the fraction of B_s(*) B_s(*) in bbar b events is
Snapshots live under flavor_catalog/references/<process_id>/. Source-line anchoring is automated; the status pill reflects match confidence, not editorial review.

branching_fraction_hflav_2024

https://hflav-eos.web.cern.ch/hflav-eos/rare/Dec2024/hflav_rare_decays_Dec24.pdf
accessed 2026-05-17 sha 0572d6a8d33f... snapshot B013/hflav_rare_decays_dec2024_bs_phi_gamma.txt AMBIGUOUS
display (34.0 +/- 3.2) x 10^-6
AMBIGUOUS
Match 1 of 2 snapshot line 14 
L11:   B(B_s0 -> phi(1020) gamma)
L12:     LHCb [206]: 33.7 +/- 1.7 +/- 3.0
L13:     Belle [205]: 36.0 +/- 5.0 +/- 7.0
L14:     HFLAV average: 34.0 +/- 3.2
L15:     PDG column: 34.2 +/- 3.6
L16: 
L17: Footnotes:
Match 2 of 2 snapshot line 15 
L12:     LHCb [206]: 33.7 +/- 1.7 +/- 3.0
L13:     Belle [205]: 36.0 +/- 5.0 +/- 7.0
L14:     HFLAV average: 34.0 +/- 3.2
L15:     PDG column: 34.2 +/- 3.6
L16: 
L17: Footnotes:
L18:   LHCb [206] uses B(B0 -> K*(892)0 gamma).
Snapshots live under flavor_catalog/references/<process_id>/. Source-line anchoring is automated; the status pill reflects match confidence, not editorial review.

branching_fraction_hflav_2024.average_inputs[0]

https://hflav-eos.web.cern.ch/hflav-eos/rare/Dec2024/hflav_rare_decays_Dec24.pdf
accessed 2026-05-17 sha 0572d6a8d33f... snapshot B013/hflav_rare_decays_dec2024_bs_phi_gamma.txt RESOLVED
fallback_value_uncertainty LHCb AAIJ 13 = (3.37 +- 0.17)e-5
RESOLVED
Match snapshot line 12 
L9: Parameter [10^-6], Measurements, Average HFLAV, PDG.
L10: 
L11:   B(B_s0 -> phi(1020) gamma)
L12:     LHCb [206]: 33.7 +/- 1.7 +/- 3.0
L13:     Belle [205]: 36.0 +/- 5.0 +/- 7.0
L14:     HFLAV average: 34.0 +/- 3.2
L15:     PDG column: 34.2 +/- 3.6
Snapshots live under flavor_catalog/references/<process_id>/. Source-line anchoring is automated; the status pill reflects match confidence, not editorial review.

branching_fraction_hflav_2024.average_inputs[1]

https://hflav-eos.web.cern.ch/hflav-eos/rare/Dec2024/hflav_rare_decays_Dec24.pdf
accessed 2026-05-17 sha 0572d6a8d33f... snapshot B013/hflav_rare_decays_dec2024_bs_phi_gamma.txt RESOLVED
fallback_value_uncertainty Belle Dutta 2014/2015 = (3.6 +- 0.5)e-5
RESOLVED
Match snapshot line 13 
L10: 
L11:   B(B_s0 -> phi(1020) gamma)
L12:     LHCb [206]: 33.7 +/- 1.7 +/- 3.0
L13:     Belle [205]: 36.0 +/- 5.0 +/- 7.0
L14:     HFLAV average: 34.0 +/- 3.2
L15:     PDG column: 34.2 +/- 3.6
L16:
Snapshots live under flavor_catalog/references/<process_id>/. Source-line anchoring is automated; the status pill reflects match confidence, not editorial review.

s_phigamma_lhcb_2019

https://arxiv.org/abs/1905.06284
accessed 2026-05-17 sha a8f9cea7df59... snapshot B013/lhcb_2019_bsphigamma_cp_arxiv.txt RESOLVED
display 0.43 +/- 0.30(stat) +/- 0.11(syst)
RESOLVED
Match snapshot line 21 
L18:   LHCb at center-of-mass energies of 7 and 8 TeV.
L19: 
L20:   Measured values:
L21:     S_phi gamma = 0.43 +/- 0.30 +/- 0.11
L22:     C_phi gamma = 0.11 +/- 0.29 +/- 0.11
L23:     A^Delta_phi gamma = -0.67 +0.37 -0.41 +/- 0.17
L24:   The first uncertainty is statistical and the second systematic. This
Snapshots live under flavor_catalog/references/<process_id>/. Source-line anchoring is automated; the status pill reflects match confidence, not editorial review.

c_phigamma_lhcb_2019

https://arxiv.org/abs/1905.06284
accessed 2026-05-17 sha a8f9cea7df59... snapshot B013/lhcb_2019_bsphigamma_cp_arxiv.txt AMBIGUOUS
display 0.11 +/- 0.29(stat) +/- 0.11(syst)
AMBIGUOUS
Match 1 of 3 snapshot line 11 
L8: Authors: LHCb Collaboration, R. Aaij et al.
L9: Report number: LHCb-PAPER-2019-015, CERN-EP-2019-077
L10: Journal reference: Phys. Rev. Lett. 123, 081802 (2019)
L11: DOI: 10.1103/PhysRevLett.123.081802
L12: 
L13: Relevant abstract extract:
L14:   A time-dependent analysis of the B_s^0 -> phi gamma decay rate is
Match 2 of 3 snapshot line 21 
L18:   LHCb at center-of-mass energies of 7 and 8 TeV.
L19: 
L20:   Measured values:
L21:     S_phi gamma = 0.43 +/- 0.30 +/- 0.11
L22:     C_phi gamma = 0.11 +/- 0.29 +/- 0.11
L23:     A^Delta_phi gamma = -0.67 +0.37 -0.41 +/- 0.17
L24:   The first uncertainty is statistical and the second systematic. This
Match 3 of 3 snapshot line 22 
L19: 
L20:   Measured values:
L21:     S_phi gamma = 0.43 +/- 0.30 +/- 0.11
L22:     C_phi gamma = 0.11 +/- 0.29 +/- 0.11
L23:     A^Delta_phi gamma = -0.67 +0.37 -0.41 +/- 0.17
L24:   The first uncertainty is statistical and the second systematic. This
L25:   is the first measurement of S and C in radiative B_s^0 decays, and
Snapshots live under flavor_catalog/references/<process_id>/. Source-line anchoring is automated; the status pill reflects match confidence, not editorial review.

a_delta_phigamma_lhcb_2019

https://arxiv.org/abs/1905.06284
accessed 2026-05-17 sha a8f9cea7df59... snapshot B013/lhcb_2019_bsphigamma_cp_arxiv.txt RESOLVED
display -0.67 +0.37 -0.41(stat) +/- 0.17(syst)
RESOLVED
Match snapshot line 23 
L20:   Measured values:
L21:     S_phi gamma = 0.43 +/- 0.30 +/- 0.11
L22:     C_phi gamma = 0.11 +/- 0.29 +/- 0.11
L23:     A^Delta_phi gamma = -0.67 +0.37 -0.41 +/- 0.17
L24:   The first uncertainty is statistical and the second systematic. This
L25:   is the first measurement of S and C in radiative B_s^0 decays, and
L26:   the results are consistent with Standard Model predictions.
Snapshots live under flavor_catalog/references/<process_id>/. Source-line anchoring is automated; the status pill reflects match confidence, not editorial review.

belle_2014_branching_fraction_input

https://arxiv.org/abs/1411.7771
accessed 2026-05-17 sha 7e36d4d73efa... snapshot B013/belle_2014_bsphigamma_arxiv.txt RESOLVED
display (3.6 +/- 0.5(stat) +/- 0.3(syst) +/- 0.6(f_s)) x 10^-5
RESOLVED
Match snapshot line 18 
L15:   B_s^0 -> phi gamma using 121.4 fb^-1 collected at the Upsilon(5S).
L16: 
L17:   B(B_s^0 -> phi gamma) =
L18:     (3.6 +/- 0.5(stat.) +/- 0.3(syst.) +/- 0.6(f_s)) x 10^-5,
L19:   where f_s is the fraction of B_s(*) B_s(*) in bbar b events.
L20: 
L21:   Belle observes no statistically significant B_s^0 -> gamma gamma
Snapshots live under flavor_catalog/references/<process_id>/. Source-line anchoring is automated; the status pill reflects match confidence, not editorial review.

lhcb_2024_tensor_fraction

https://arxiv.org/abs/2406.00235
accessed 2026-05-17 sha 7cbfba098c45... snapshot B013/lhcb_2024_bskkgamma_arxiv.txt RESOLVED
display 16.8 +/- 0.5(stat) +/- 0.7(syst)%
RESOLVED
Match snapshot line 19 
L16:   accounts for almost 70% of the decay rate.
L17: 
L18:   The overall tensor contribution is measured as
L19:     F_{f2} = 16.8 +/- 0.5(stat.) +/- 0.7(syst.)%.
L20: 
L21:   For the preferred solution,
L22:     B(B_s^0 -> f2'(1525) gamma) / B(B_s^0 -> phi gamma)
Snapshots live under flavor_catalog/references/<process_id>/. Source-line anchoring is automated; the status pill reflects match confidence, not editorial review.

lhcb_2024_f2prime_ratio

https://arxiv.org/abs/2406.00235
accessed 2026-05-17 sha 7cbfba098c45... snapshot B013/lhcb_2024_bskkgamma_arxiv.txt RESOLVED
display 19.4 +0.9 -0.8(stat) +1.4 -0.5(syst) +/- 0.5(B)%
RESOLVED
Match snapshot line 23 
L20: 
L21:   For the preferred solution,
L22:     B(B_s^0 -> f2'(1525) gamma) / B(B_s^0 -> phi gamma)
L23:     = 19.4 +0.9 -0.8(stat.) +1.4 -0.5(syst.) +/- 0.5(B)%.
L24:   This is the first observation of B_s^0 -> f2'(1525) gamma.
Snapshots live under flavor_catalog/references/<process_id>/. Source-line anchoring is automated; the status pill reflects match confidence, not editorial review.

lhcb_2024_phi_ee_at2

https://arxiv.org/abs/2411.10219
accessed 2026-05-17 sha 99613e7d4a48... snapshot B013/lhcb_2024_bsphiee_arxiv.txt RESOLVED
display -0.045 +/- 0.235(stat) +/- 0.014(syst)
RESOLVED
Match snapshot line 23 
L20:   to be less than 11.5% at 90% confidence level.
L21: 
L22:   A_T^{Re CP} = 0.116 +/- 0.155 +/- 0.006.
L23:   A_T^{(2)} = -0.045 +/- 0.235 +/- 0.014.
L24:   A_T^{Im CP} = 0.002 +/- 0.247 +/- 0.016.
L25:   The transverse asymmetries are sensitive to virtual-photon
L26:   polarisation and are consistent with Standard Model predictions.
Snapshots live under flavor_catalog/references/<process_id>/. Source-line anchoring is automated; the status pill reflects match confidence, not editorial review.

lhcb_2024_phi_ee_atimcp

https://arxiv.org/abs/2411.10219
accessed 2026-05-17 sha 99613e7d4a48... snapshot B013/lhcb_2024_bsphiee_arxiv.txt RESOLVED
display 0.002 +/- 0.247(stat) +/- 0.016(syst)
RESOLVED
Match snapshot line 24 
L21: 
L22:   A_T^{Re CP} = 0.116 +/- 0.155 +/- 0.006.
L23:   A_T^{(2)} = -0.045 +/- 0.235 +/- 0.014.
L24:   A_T^{Im CP} = 0.002 +/- 0.247 +/- 0.016.
L25:   The transverse asymmetries are sensitive to virtual-photon
L26:   polarisation and are consistent with Standard Model predictions.
Snapshots live under flavor_catalog/references/<process_id>/. Source-line anchoring is automated; the status pill reflects match confidence, not editorial review.

lhcb_2024_phi_ee_fl_limit

https://arxiv.org/abs/2411.10219
accessed 2026-05-17 sha 99613e7d4a48... snapshot B013/lhcb_2024_bsphiee_arxiv.txt RESOLVED
display < 11.5% at 90% CL
RESOLVED
Match snapshot line 20 
L17:   0.0009 to 0.2615 GeV^2/c^4.
L18: 
L19:   The longitudinal polarisation fraction of the phi meson is measured
L20:   to be less than 11.5% at 90% confidence level.
L21: 
L22:   A_T^{Re CP} = 0.116 +/- 0.155 +/- 0.006.
L23:   A_T^{(2)} = -0.045 +/- 0.235 +/- 0.014.
Snapshots live under flavor_catalog/references/<process_id>/. Source-line anchoring is automated; the status pill reflects match confidence, not editorial review.