Constraining new physics with B to K* mu+ mu- in the early LHC era

Aoife Bharucha; William Reece

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Constraining new physics with B to K* mu+ mu- in the early LHC era

Aoife Bharucha, William Reece

High Energy Physics - Phenomenology · Submitted 23 Feb 2010

abstract compiled · 2026-09-23 · no language-model review

The authors' main claim Two of these are well known in the experimental community; however, we show that measuring S5 adds complementary sensitivity to physics beyond the Standard model.

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What the abstract itself states, as probabilities: claims first 0.05 · states limitation 0.67 · human participants 0.02 · controlled comparison 0.10 · randomized assignment 0.01 · states quantitative result 0.47 · compares with prior results 0.66 · mentions code or data availability 0.15.

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arXiv listing abstract v2. Results and the main claim are underlined; show every role.

We investigate the observables available in the angular distribution of B to K* mu+ mu- to identify those suitable for measurements in the first few years of LHC data taking. As experimental uncertainties will dominate, we focus on observables that are simple to measure, while maximizing the potential for discovery. There are three observables that may be extracted by counting signal events as a function of one or two decay angles and correspond to large features of the full angular distribution in the Standard Model: Afb, Fl, and S5. Two of these are well known in the experimental community; however, we show that measuring S5 adds complementary sensitivity to physics beyond the Standard model. Like Afb, it features a zero-crossing point with reduced hadronic uncertainties at leading order and in the large recoil limit. We explore the experimental sensitivity to this point at LHCb and show that it may be measured with high precision due to the steepness of the S5 distribution. Current experimental model independent constraints on parameter space are presented and predictions made for the values of the Afb and S5 zero-crossing points. The relative impact of LHCb measurements of Afb, Fl, and S5, with 2 fb^(-1) of integrated luminosity, is assessed. These issues are explored with a new model of the decay that can be used with standard simulation tools such as EVTGEN.

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What the classifier reports for each sentence. The number is the probability it gave the label.
#	sentence	role	the authors' own work	states the main conclusion	strength
s0	We investigate the observables available in the angular distribution of B to K* mu+ mu- to identify those suitable for measurements in the first few years of LHC data taking.	contribution 0.99	0.87	0.06	asserted 0.88
s1	As experimental uncertainties will dominate, we focus on observables that are simple to measure, while maximizing the potential for discovery.	method 0.67	0.52	0.05	asserted 0.98
s2	There are three observables that may be extracted by counting signal events as a function of one or two decay angles and correspond to large features of the full angular distribution in the Standard Model: Afb, Fl, and S5.	contribution 0.60	0.51	0.13	hedged possibility 0.93
s3	Two of these are well known in the experimental community; however, we show that measuring S5 adds complementary sensitivity to physics beyond the Standard model.	contribution 0.85	0.87	0.25	asserted 1.00
s4	Like Afb, it features a zero-crossing point with reduced hadronic uncertainties at leading order and in the large recoil limit.	interpretation 0.33	0.35	0.09	asserted 1.00
s5	We explore the experimental sensitivity to this point at LHCb and show that it may be measured with high precision due to the steepness of the S5 distribution.	result 0.67	0.81	0.14	hedged possibility 0.97
s6	Current experimental model independent constraints on parameter space are presented and predictions made for the values of the Afb and S5 zero-crossing points.	result 0.52	0.77	0.12	asserted 0.96
s7	The relative impact of LHCb measurements of Afb, Fl, and S5, with 2 fb^(-1) of integrated luminosity, is assessed.	contribution 0.75	0.81	0.10	asserted 0.81
s8	These issues are explored with a new model of the decay that can be used with standard simulation tools such as EVTGEN.	method 0.83	0.70	0.03	asserted 0.93

What kind of paper the classifier reports this is: theoretical result 0.38 · evidence from simulation or computation 0.75.

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The paper

Original abstract

We investigate the observables available in the angular distribution of B to K* mu+ mu- to identify those suitable for measurements in the first few years of LHC data taking. As experimental uncertainties will dominate, we focus on observables that are simple to measure, while maximizing the potential for discovery. There are three observables that may be extracted by counting signal events as a function of one or two decay angles and correspond to large features of the full angular distribution in the Standard Model: Afb, Fl, and S5. Two of these are well known in the experimental community; however, we show that measuring S5 adds complementary sensitivity to physics beyond the Standard model. Like Afb, it features a zero-crossing point with reduced hadronic uncertainties at leading order and in the large recoil limit. We explore the experimental sensitivity to this point at LHCb and show that it may be measured with high precision due to the steepness of the S5 distribution. Current experimental model independent constraints on parameter space are presented and predictions made for the values of the Afb and S5 zero-crossing points. The relative impact of LHCb measurements of Afb, Fl, and S5, with 2 fb^(-1) of integrated luminosity, is assessed. These issues are explored with a new model of the decay that can be used with standard simulation tools such as EVTGEN.

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References

Forward citations

Cited by 12 Pith papers

Reviewed papers in the Pith corpus that reference this work. Sorted by Pith novelty score. Full citation record

On B -> V l l at small dilepton invariant mass, power corrections, and new physics
hep-ph 2012-12 conditional novelty 6.0 of 10

The positive-helicity amplitudes in B to K* lepton pairs are suppressed by the V-A structure even including non-factorizable charm and light-quark corrections, leaving P1 and P3^CP as clean null tests sensitive to C'_...
Complete Anatomy of B -> K*ll and its angular distribution
hep-ph 2012-02 accept novelty 6.0 of 10

A complete basis of angular observables for B -> K* l+ l- is constructed, with six form-factor-independent observables in the massless case plus two for lepton masses and two for scalars.
New physics reach of the decay mode $\bar{B} \to \bar{K}^{*0}\ell^+\ell^-$
hep-ph 2010-05 accept novelty 6.0 of 10

The angular distribution of B to K*0 l+ l- has four symmetries in the massless-lepton limit, not three, and this yields one exact constraint among the angular coefficients plus a new form-factor-free observable.
Bayesian Fit of Exclusive $b \to s \bar\ell\ell$ Decays: The Standard Model Operator Basis
hep-ph 2012-05 conditional novelty 5.0 of 10

A full Bayesian fit of the Wilson coefficients C7, C9 and C10 to exclusive rare B decays finds a Standard-Model-like and a sign-flipped solution with roughly equal posterior weight, and no evidence requiring new physics.
Model-independent constraints on new physics in b --> s transitions
hep-ph 2011-11 conditional novelty 5.0 of 10

Combining all available b to s rare-decay data, the fit finds every 95% confidence region compatible with the Standard Model, excludes several sign-flipped Wilson coefficient scenarios, and caps Bs to mu mu at roughly...

Show 7 more citing papers

On transverse asymmetries in B --> K* l+l-
hep-ph 2011-06 accept novelty 5.0 of 10

A new transverse asymmetry A_T^(re) is defined for B to K* l+ l-, and the zero-crossing patterns of three independent asymmetries are shown to discriminate among new-physics scenarios in C7, C9, and C10.
Exploring New Physics in the C7-C7' plane
hep-ph 2011-04 conditional novelty 5.0 of 10

The isospin asymmetry in B to K* gamma excludes the flipped-sign solution for the Wilson coefficient C7 at one sigma, requiring a 1.6 sigma stretch to keep it alive.
New Physics in b -> s mu+ mu-: CP-Conserving Observables
hep-ph 2010-08 accept novelty 5.0 of 10

New vector-axial-vector operators can push most CP-conserving asymmetries in b to s mu mu decays well past Standard Model predictions, while scalar and tensor operators can do so only for the forward-backward asymmetr...
The Benefits of B ---> K* l+ l- Decays at Low Recoil
hep-ph 2010-06 conditional novelty 5.0 of 10

Low-recoil B -> K* l+ l- data, analyzed in the Grinstein-Pirjol HQET framework, constrain the Wilson coefficients C9 and C10 more tightly than large-recoil data and admit both Standard Model and beyond-Standard-Model ...
Theoretical and Phenomenological Constraints on Form Factors for Radiative and Semi-Leptonic B-Meson Decays
hep-ph 2010-04 accept novelty 5.0 of 10

Two-term series expansions, constrained by newly computed NLO tensor-current dispersive bounds, describe B to K, rho, K* and phi form factors across the whole decay region and reproduce lattice points not used in the fits.
Status of the $B\to K^*\mu^+\mu^-$ anomaly after Moriond 2017
hep-ph 2017-03 accept novelty 4.0 of 10

Combining updated LHCb, ATLAS and CMS data, the b to s mu mu anomalies remain at 5.2 sigma and are fit by a new-physics shift in C9 of about minus one, with no evidence for q-squared or helicity dependence.
Implications of LHCb measurements and future prospects
hep-ex 2012-08 accept novelty 4.0 of 10

LHCb's first 1.0 fb^-1 of 7 TeV data already constrain several new-physics scenarios, and a proposed upgrade to 50 fb^-1 would sharpen those constraints by roughly an order of magnitude.

How the literature uses it

16 arXiv papers cite this in 19 sentences

Each citing sentence is taken from the citing paper's LaTeX source and typed by Pith's classifier. A label appears at probability 0.8 or more (0.95 for support), a contest at 0.7 or more; the quoted words are the citing authors'. How each label was checked · JSON

Papers citing it · 13 sentences without a confident label

Cites it as background 6 papers

Suitable combinations of these observables have also been identified that have either $i)$ reduced hadronic uncertainties and possibly higher sensitivities to BSM contributions [ref] ; or $ii)$ become short-distance independent, allowing one to gain information on form factors [ref] .

Bayesian Fit of Exclusive $b \to s \bar\ell\ell$ Decays: The Standard Model Operator Basis · Introduction · 0.80
A study of those observables relevant for the first few may be found in [ref] .

New physics reach of the decay mode $\bar{B} \to \bar{K}^{*0}\ell^+\ell^-$ · Introduction · 0.84
Because of these virtues, theoretical research interests in this mode have exploded and the precision is highly improved, see Refs. [ref] for an incomplete list.

Branching ratios, forward-backward asymmetries and angular distributions of $B\to K_2^*l^+l^-$ in the standard model and new physics scenarios · Introduction · 0.88

What it cites · 44 sentences without a confident label

Builds on 1 paper

The auxiliary functions $A$-$I(q^2)$ follow [ref] ; however, we have updated the previous expressions to include additional primed, scalar, and pseudoscalar operators, as well as QCDF correction via $𝒯^(')NLO_∥(q^2)$ and $𝒯^(')NLO_⊥(q^2)$ as outlined in [ref].

A Comparative Study of the Decays $B \to (K,K^*) \ell^+ \ell^-$ in Standard Model and Supersymmetric Theories · Decay Amplitude · 0.94

Uses the method or tool of 11 papers

These corrections are included in the definitions of $𝒯_∥(q^2)$ and $𝒯_⊥(q^2)$ found in [ref] and are given in terms of $ξ_⊥$ and $ξ_∥$; however, $𝒪(α_s)$ factorizable corrections that arise from expressing the full form factors in terms of $ξ_⊥$ and $ξ_∥$ must then be subsumed.

Systematic approach to exclusive B ->V l^+l^-, V gamma decays · QCD Factorization Corrections · 0.80
Following [ref] , the mean, one and two sigma contours could then be found from these results.

New observables in the decay mode anti-B --> anti-K*0 l+ l- · Results · 0.95
Following [ref] , we instead express our LO results for the decay amplitude in terms of the full form factors.

Symmetries and Asymmetries of B -> K* mu+ mu- Decays in the Standard Model and Beyond · QCD Factorization Corrections · 0.93

Uses data or values from 12 papers

We use the full set of LCSR form factors in our model [ref] , where the sum rules for all form factors except for $A_0$ were calculated at $𝒪(α_s)$ accuracy for twist-2 and-3 and tree-level accuracy for twist-4 contributions.

B_{d,s}->rho, omega, K*, phi Decay Form Factors from Light-Cone Sum Rules Revisited · Form Factors · 0.82
The Wilson coefficients we use are close to the scenario GMSSM IV in [ref] , corresponding to large NP contributions to both 7 and 7 allowed by existing experimental bounds (see [ref]).

Symmetries and Asymmetries of B -> K* mu+ mu- Decays in the Standard Model and Beyond · Overview of Specific Models and Effects on Wilson Coefficients · 0.94
Recently has made a measurement of the forward-backward asymmetry, and finds the integrated $A_FB$ value in the region 1-6$GeV^2$ to be $-0.26±0.29$ [ref] .

Measurement of the Differential Branching Fraction and Forward-Backword Asymmetry for B->K(*)l+l- · Constraints · 0.98

Compares with 6 papers

[ref] can be compared to 2 from [ref] , in which 7 and 7 are assumed to be real and all other Wilson coefficients SM-like.

CP Asymmetries in bar B -> bar K* (-> bar K pi) l+ l- and Untagged bar B_s,B_s -> phi (-> K+ K-) l+ l- Decays at NLO · Constraints · 0.96
We present our theoretical framework in a way that allows direct comparison with [ref] , by expressing the decay amplitude in terms of the auxiliary functions used in that reference.

A Comparative Study of the Decays $B \to (K,K^*) \ell^+ \ell^-$ in Standard Model and Supersymmetric Theories · Introduction · 0.93
The estimated experimental uncertainties are of a similar size to the current theoretical uncertainties, and much smaller than the current experimental constraints [ref] .

Measurement of the Differential Branching Fraction and Forward-Backword Asymmetry for B->K(*)l+l- · Integrated Quantities · 0.81

Cites as support 2 papers

Enhancements to 7 and 9 in the presence of NP phases can, however, be sizable [ref] and could, in principle, lead to reasonable experimental resolutions, particularly for 9.

CP Asymmetries in bar B -> bar K* (-> bar K pi) l+ l- and Untagged bar B_s,B_s -> phi (-> K+ K-) l+ l- Decays at NLO · Observables · 0.96
This was shown explicitly for the MSSM in [ref] .

Analysis of Neutral Higgs-Boson Contributions to the Decays B_s -> l^+l^- and B -> K l^+l^- · Wilson Coefficients · 1.00

Cites as background 18 papers

Their definition in terms of hadronic matrix elements can be found, for example, in [ref] .

B_{d,s}->rho, omega, K*, phi Decay Form Factors from Light-Cone Sum Rules Revisited · Form Factors · 0.97
The properties of the full-angular distribution have been studied by many authors and a number of potential measurements have been identified; e.g. [ref] .

CP Asymmetries in bar B -> bar K* (-> bar K pi) l+ l- and Untagged bar B_s,B_s -> phi (-> K+ K-) l+ l- Decays at NLO · Introduction · 0.93
The properties of the full-angular distribution have been studied by many authors and a number of potential measurements have been identified; e.g. [ref] .

Short Distance Coefficients and the Vanishing of the Lepton Asymmetry in $B\to V\ell^+\ell^-$ · Introduction · 0.93

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