Recognition: no theorem link
Search for the decays B_{(s)}⁰to J/psiγ at LHCb
Pith reviewed 2026-05-13 18:54 UTC · model grok-4.3
The pith
LHCb sets upper limits of 2.9×10^{-6} and 2.5×10^{-6} on the branching fractions for Bs0 and B0 decays to J/ψγ at 90% CL.
A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.
Core claim
Using 3 fb^{-1} of data at 7 and 8 TeV plus 6 fb^{-1} at 13 TeV, no evidence for either B_s^0 → J/ψγ or B^0 → J/ψγ is found. Assuming no contribution from the B^0 mode yields an upper limit B(B_s^0 → J/ψγ) < 2.9 × 10^{-6} at 90% confidence level. Assuming instead no contribution from the B_s^0 mode gives B(B^0 → J/ψγ) < 2.5 × 10^{-6} at 90% CL. These bounds supersede previous LHCb results.
What carries the argument
Invariant-mass fits to J/ψγ candidates extracted from the full LHCb detector dataset, with signal shapes from simulation and backgrounds modeled from control samples and sidebands.
If this is right
- The new limits constrain theoretical models that predict enhanced rates for these decays through new physics contributions.
- Improved precision on both modes allows more direct comparison with Standard Model calculations of rare radiative B decays.
- The mutual-exclusion approach to limit setting provides independent bounds that can be combined with other B-physics measurements.
- Future LHCb datasets will be able to push the limits lower or potentially observe the decays if their rates lie near the current bounds.
Where Pith is reading between the lines
- These limits can be folded into global fits of new-physics parameters alongside other flavor-changing neutral-current processes.
- If both decay modes are present at comparable rates, a joint fit on larger datasets could separate their contributions.
- The analysis techniques developed here for photon reconstruction in the forward spectrometer can be applied to other rare B decays involving photons.
- Non-observation at this sensitivity level strengthens the case for measuring related modes such as B to J/ψ plus other light particles.
Load-bearing premise
Background shapes and efficiencies are accurately modeled from simulation and control samples without unexpected contributions from other rare processes or detector effects that could mimic the signal.
What would settle it
A statistically significant excess of events in the signal mass window that corresponds to a branching fraction exceeding either reported upper limit.
Figures
read the original abstract
A search for the rare decays $B_{(s)}^0\to J/\psi\gamma$ is performed with proton-proton collision data collected by the LHCb experiment, corresponding to integrated luminosities of $3~\rm{fb}^{-1}$ at centre-of-mass energies of 7 and 8 TeV, and $6~\rm{fb}^{-1}$ at 13 TeV. Assuming no contribution from $B^0\to J/\psi\gamma$ decay, an upper limit is set on the branching fraction $\mathcal{B}(B_{s}^0\to J/\psi\gamma)<2.9\times10^{-6}$ at the 90% confidence level. If instead no contribution from $B_{s}^0\to J/\psi\gamma$ decay is assumed, the limit is $\mathcal{B}(B^0\to J/\psi\gamma)<2.5\times10^{-6}$ at the 90% confidence level. These results supersede the previous LHCb results, with the limit for $B_{s}^0\to J/\psi\gamma$ improved by a factor of 2.5.
Editorial analysis
A structured set of objections, weighed in public.
Referee Report
Summary. The manuscript reports a search for the rare decays B_s^0 → J/ψγ and B^0 → J/ψγ in proton-proton collision data collected by LHCb, corresponding to 3 fb^{-1} at √s = 7 and 8 TeV plus 6 fb^{-1} at 13 TeV. Assuming no contribution from the B^0 mode, an upper limit B(B_s^0 → J/ψγ) < 2.9 × 10^{-6} is set at 90% CL; assuming no B_s^0 contribution yields B(B^0 → J/ψγ) < 2.5 × 10^{-6} at 90% CL. The results supersede prior LHCb limits, with a factor of 2.5 improvement for the B_s^0 channel, and are extracted from a fit to the reconstructed B-candidate invariant mass using simulation for signal shape and efficiency (corrected via control samples) together with data-driven background modeling.
Significance. If the results hold, they furnish the tightest existing upper bounds on these branching fractions, which probe the b → sγ transition and potential new-physics enhancements. The analysis follows the standard LHCb pipeline for rare-decay searches, with the 90% CL limits derived directly from the data and Monte Carlo efficiencies without circular normalization. The improvement in sensitivity from the enlarged dataset is quantitatively meaningful for constraining theoretical models.
minor comments (1)
- [Abstract] Abstract: the total integrated luminosity is stated as separate 3 fb^{-1} and 6 fb^{-1} blocks; a single combined figure (9 fb^{-1}) would improve immediate readability.
Simulated Author's Rebuttal
We thank the referee for their positive assessment of the manuscript and for recommending acceptance. The report identifies no major comments requiring a point-by-point response.
Circularity Check
No significant circularity; limits derived from data fit
full rationale
The paper sets upper limits on rare branching fractions from a fit to LHCb collision data in the B candidate mass. Signal shapes and efficiencies come from simulation corrected by control samples; backgrounds are modeled from data sidebands. No self-referential equations, fitted inputs renamed as predictions, or load-bearing self-citation chains appear in the central statistical procedure. The result is self-contained against the input dataset and does not reduce to its assumptions by construction.
Axiom & Free-Parameter Ledger
axioms (2)
- domain assumption Standard Model branching fraction predictions and decay kinematics for B mesons
- domain assumption Accurate modeling of detector efficiencies and backgrounds from simulation and control samples
Reference graph
Works this paper leans on
- [1]
-
[2]
Y. Li and C.-D. L ¨ u,Annihilation-type radiative decays of B meson in perturbative QCD approach, Phys. Rev.D74(2006) 097502,arXiv:hep-ph/0605220
-
[3]
A. Kozachuk, D. Melikhov, and N. Nikitin,Annihilation-type rare radiative B(s) →V γ decays, Phys. Rev.D93(2016) 014015,arXiv:1511.03540
-
[4]
L.-S. Geng and E. Oset,Novel nonperturbative approach for radiative ¯B0( ¯B0 s) →J/ψγ decays, Phys. Rev.D94(2016) 014018,arXiv:1512.08563
- [5]
-
[6]
Aubertet al.,Search for the decay B0 →J/ψγ , Phys
BaBar collaboration, B. Aubertet al.,Search for the decay B0 →J/ψγ , Phys. Rev. D70(2004) 091104,arXiv:hep-ex/0408018
-
[7]
Aaijet al.,Search for the decays B0 →J/ ψγ and B0 s →J/ ψγ, Phys
LHCb collaboration, R. Aaijet al.,Search for the decays B0 →J/ ψγ and B0 s →J/ ψγ, Phys. Rev.D92(2015) 112002,arXiv:1510.04866. 10
-
[8]
LHCb collaboration, A. A. Alves Jr.et al.,The LHCb detector at the LHC, JINST3 (2008) S08005
work page 2008
-
[9]
Aaijet al.,LHCb detector performance, Int
LHCb collaboration, R. Aaijet al.,LHCb detector performance, Int. J. Mod. Phys. A30(2015) 1530022,arXiv:1412.6352
-
[10]
Aaijet al.,Performance of the LHCb Vertex Locator, JINST9(2014) P09007, arXiv:1405.7808
R. Aaijet al.,Performance of the LHCb Vertex Locator, JINST9(2014) P09007, arXiv:1405.7808
-
[11]
Arinket al.,Performance of the LHCb Outer Tracker, JINST9(2014) P01002, arXiv:1311.3893
R. Arinket al.,Performance of the LHCb Outer Tracker, JINST9(2014) P01002, arXiv:1311.3893
-
[12]
P. d’Argentet al.,Improved performance of the LHCb Outer Tracker in LHC Run 2, JINST12(2017) P11016,arXiv:1708.00819
- [13]
-
[14]
Aaijet al.,The LHCb trigger and its performance in 2011, JINST8(2013) P04022, arXiv:1211.3055
R. Aaijet al.,The LHCb trigger and its performance in 2011, JINST8(2013) P04022, arXiv:1211.3055
-
[15]
R. Aaijet al.,Design and performance of the LHCb trigger and full real-time recon- struction in Run 2 of the LHC, JINST14(2019) P04013,arXiv:1812.10790
-
[16]
N. Grieseret al.,The LHCb stripping project: Sustainable legacy data processing for high-energy physics, Comput. Softw. Big. Sci.9(2025) 21,arXiv:2509.05294
-
[17]
A Brief Introduction to PYTHIA 8.1
T. Sj¨ ostrand, S. Mrenna, and P. Skands,A brief introduction to PYTHIA 8.1, Comput. Phys. Commun.178(2008) 852,arXiv:0710.3820
work page internal anchor Pith review Pith/arXiv arXiv 2008
-
[18]
I. Belyaevet al.,Handling of the generation of primary events in Gauss, the LHCb simulation framework, J. Phys. Conf. Ser.331(2011) 032047
work page 2011
-
[19]
D. J. Lange,The EvtGen particle decay simulation package, Nucl. Instrum. Meth. A462(2001) 152
work page 2001
-
[20]
N. Davidson, T. Przedzinski, and Z. Was,PHOTOS interface in C++: Technical and physics documentation, Comput. Phys. Commun.199(2016) 86, arXiv:1011.0937
-
[21]
Allisonet al.,Geant4 developments and applications, IEEE Trans
Geant4 collaboration, J. Allisonet al.,Geant4 developments and applications, IEEE Trans. Nucl. Sci.53(2006) 270
work page 2006
-
[22]
Clemencicet al.,The LHCb simulation application, Gauss: Design, evolution and experience, J
M. Clemencicet al.,The LHCb simulation application, Gauss: Design, evolution and experience, J. Phys. Conf. Ser.331(2011) 032023
work page 2011
-
[23]
LHCb collaboration, R. Aaijet al.,Measurement of the relative rate of prompt χc0, χc1 andχ c2 production at √s=7 TeV, JHEP10(2013) 115,arXiv:1307.4285
-
[24]
LHCb collaboration, R. Aaijet al.,Measurement of the track reconstruction efficiency at LHCb, JINST10(2015) P02007,arXiv:1408.1251
- [25]
-
[26]
Navaset al.,Review of particle physics, Phys
Particle Data Group, S. Navaset al.,Review of particle physics, Phys. Rev.D110 (2024) 030001
work page 2024
-
[27]
L. Breiman, J. H. Friedman, R. A. Olshen, and C. J. Stone,Classification and regression trees, Wadsworth international group, Belmont, California, USA, 1984
work page 1984
-
[28]
Y. Freund and R. E. Schapire,A decision-theoretic generalization of on-line learning and an application to boosting, J. Comput. Syst. Sci.55(1997) 119
work page 1997
-
[29]
A. Blum, A. Kalai, and J. Langford,Beating the hold-out: bounds for k-fold and progressive cross-validation, inProceedings of the Twelfth Annual Conference on Com- putational Learning Theory, COLT ’99, (New York, NY, USA), 203–208, Association for Computing Machinery, 1999
work page 1999
-
[30]
Sensitivity of searches for new signals and its optimization
G. Punzi,Sensitivity of searches for new signals and its optimization, eConfC030908 (2003) MODT002,arXiv:physics/0308063
work page internal anchor Pith review Pith/arXiv arXiv 2003
-
[31]
LHCb collaboration, R. Aaijet al.,Precise measurement of the fs/fd ratio of frag- mentation fractions and of B0 s decay branching fractions, Phys. Rev.D104(2021) 032005,arXiv:2103.06810
-
[32]
T. Skwarnicki,A study of the radiative cascade transitions between the Upsilon-prime and Upsilon resonances, PhD thesis, Institute of Nuclear Physics, Krakow, 1986, DESY-F31-86-02
work page 1986
-
[33]
Albrechtet al.,Search for hadronic b→u decays, Phys
ARGUS collaboration, H. Albrechtet al.,Search for hadronic b→u decays, Phys. Lett.B241(1990) 278
work page 1990
-
[34]
Belle II collaboration, I. Adachiet al.,Observation of time-dependent CP violation and measurement of the branching fraction of B0 →J/ ψπ0 decays, Phys. Rev.D111 (2025) 012011,arXiv:2410.08622
-
[35]
LHCb collaboration, R. Aaijet al.,Improved measurement of η/η ′ mixing in B0 (s) → J/ψη (′) decays, JHEP10(2025) 113,arXiv:2507.13914
-
[36]
A. L. Read,Presentation of search results: The CL s technique, J. Phys.G28(2002) 2693
work page 2002
-
[37]
Confidence Level Computation for Combining Searches with Small Statistics
T. Junk,Confidence level computation for combining searches with small statistics, Nucl. Instrum. Meth.A434(1999) 435,arXiv:hep-ex/9902006. 12 LHCb collaboration R. Aaij38 , M. Abdelfatah 69, A.S.W. Abdelmotteleb 57 , C. Abellan Beteta 51 , F. Abudin´ en59 , T. Ackernley61 , A. A. Adefisoye 69 , B. Adeva47 , M. Adinolfi 55 , P. Adlarson87 , C. Agapopoulou...
work page Pith review arXiv 1999
discussion (0)
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