New Physics in B-meson decays

Transcription

1 New Physics in B-meson decays A flavorful study in scarlet Avelino Vicente IFIC CSIC / U. Valencia Laboratori Nazionali di Frascati Theory Group seminar 1

2 Before the LHC started operating we all hoped for great discoveries... 2

3 Microscopic black holes Extra dimensions Supersymmetry Compositeness LHC expectations

4 LHC results GeV palm tree

5 LHC results GeV palm tree B-meson anomalies A mirage?

6 Outline The facts Anomalies in B-meson decays The suspects New physics explanations of the anomalies My favorite suspect Boucenna, Celis, Fuentes-Martin, AV, Virto [ , ] 6

7 The facts

8 The anomalies Episode 1 [LHCb, 2013] , , : First anomalies found by LHCb Data collected: Decrease (w.r.t. the SM) in several branching ratios Several anomalies in angular observables arxiv:

9 The anomalies differential angular distribution Optimized observables [Descotes-Genon et al, 2012, 2013] [Figure borrowed from Javier Virto] 9

10 The anomalies [LHCb, 2014] arxiv: Episode : Lepton universality violation [Hiller, Kruger, 2004] 10

11 The anomalies Episode 3 [LHCb, 2015] C. Langenbruch, Moriond 2015 March 20th 2015 : LHCb confirms first anomalies [ Complete LHC Run I dataset ] Errors shrunk anomalies persist 11

12 Interpreting the anomalies Effective hamiltonian : Wilson coefficients : Operators [ analogous for primed operators ] 12

13 David Straub's talk Moriond 2015

14 Table from Descotes-Genon et al,

15 d e te n Ju tda m ou o fr dy Composite Higgs Z' boson e a d realtmannshofer, Aristizabal Sierra, Buras, Girrbach-Noe, li S Al Buras, Celis, Crivellin, D' Niehoff, Stangl, Straub The Other Calibbi, Crivellin, Greljo, Isidori, Marzocca, Ota Model building anomalies Ambrosio, Fuentes-Martín, Gauld, Girrbach-Noe, Goertz, Gori, Haisch, Heeck, Jung, Niehoff, Pospelov, Serôdio, Staub, Straub, Vicente, Yavin Leptoquarks Alonso, Becirevic, Biswas, Chowdhuri, de Medeiros Varzielas, Fajfer, Grinstein, Gripaios, Han, Hiller, Kosnik, Lee, Martin Camalich, Mohanta, Nardecchia, Renner, Sahoo, Schmaltz SM uncertainties Global fits Alonso, Altmannshofer, Beaujean, Bobeth, DescotesGenon, Egede, Ghosh, Grinstein, Hiller, Hurth, Mahmoudi, Martin Camalich, Matias, Nardecchia, Neshatpour, Patel, Petridis, Renner, Schmaltz, Straub, van Dyk, Virto anomalies Altmannshofer, Bharucha, Descotes-Genon, Ghosh, Hiller, Hofer, Horgan, Hurth, Jaeger, Liu, Lyon, Martin Camalich, Matias, Meinel, Straub, Virto, Wingate, Zwicky Implications - LFV Bhattacharya, Boucenna, Civellin, Datta, de Medeiros Varzielas, Glashow, Gripaios, Guadagnoli, Hiller, Hofer, Kane, Lee, London, Matias, Mohanta, Nardecchia, Nierste, Pokorski, Renner, Rosiek, Sahoo, Shivashankara, Tandean, Valle, Vicente 15

16 The anomalies BaBar + Belle + LHCb Another hint of lepton universality violation? Deviation from the SM at the 4 s level 16

17 The anomalies 17

18 Remarks about the anomalies The b s anomalies in angular distributions and branching ratios can be faked by hadronic effects A matter of hot debate However, ratios such as RK and R(D(*)) are theoretically clean and cannot be explained with hadronic physics Hadronic effects are lepton universal! The C9μ coefficient seems to play a key role in the b s anomalies Preference for left-handed quark neutral currents Current data are compatible with universal scaling in R(D) and R(D*) This is guaranteed by a left-handed charged current 18

19 The suspects

20 New Physics explanations Neutral current Z boson, leptoquarks, compositeness, RPV loops Charged current Charged Higgs, leptoquarks, compositeness, W boson, RPV sfermions + EFTs, of course 20

21 Z : what do we need? Z' model building Easiest (but not unique) solution List of ingredients : A Z' boson that contributes to (and optionally to The Z' must have flavor violating couplings to quarks The Z' must have non-universal couplings to leptons ) Optional (but highly desirable!): interplay with some other physics 21

22 A model with a dark sector [Aristizabal Sierra, Staub, AV, 2015] Vector-like = joker for model builders Vector-like fermions Link to SM fermions Scalars breaking Dark matter candidate 22

23 A model with a dark sector [Aristizabal Sierra, Staub, AV, 2015] Vector-like = joker for model builders Vector-like (Dirac) masses VL SM mixing 23

24 Solving the anomalies Similar to Altmannshofer et al, Crivellin et al, 2014 [Aristizabal Sierra, Staub, AV, 2015] Direct Z couplings also possible Altmannshofer et al, 2014, Crivellin et al, 2014, 2015 [Lm Lt], Celis et al, 2015 [BGL],... 24

25 Charged Higgs and R(D * ) ( ) Natural candidate for the b c anomalies: a charged Higgs But the standard 2HDMs do not work [Celis et al, 2012] Type II 2HDM Aligned 2HDM [BaBar collaboration, 2012] [Celis et al, 2012] However: a general Type III 2HDM can do the job [Crivellin et al, 2012] 25

26 Killing two birds with one stone What if the two anomalies are hinting at the same New Physics? A common NP framework Chuck Norris fact of the day EFTs: [Bhattacharya et al, 2014, Alonso et al, Calibbi et al, Greljo et al, 2015] Chuck Norris can kill two stones with one bird 26

27 Leptoquarks Simultaneous explanation of RK and R(D*) puzzles: leptoquarks? Candidates in the literature Vm = (3,1,-2/3) F = (3,1,-1/3) Alonso, Grinstein, Martin-Camalich Bauer, Neubert [ ] [ , ] Barbieri, Isidori, Pattori, Senia Das, Hati, Kumar, Mahajan [ ] [ ] Same as in RPV SUSY Deshpande, He [ ] One leptoquark to rule them all [ ] Vm = (3,3,2/3) Fajfer, Kosnik [ ] See also Deppisch, Kulkarni, Päs, Schumacher [ ] for a possible connection to neutrino masses 27

28 Strongly-coupled NP Buttazzo, Greljo, Isidori, Marzocca [ ] SM mix TC baryons SU(NTC) Vector-like TC quarks Lowest-lying vector meson resonances I prefer something more... elementary RK and R(D(*)) 28

29 My favorite suspect

30 My favorite suspect Towards a gauge model The model I The model II Numerical results 30

31 Towards a gauge explanation of the anomalies Flavor violating couplings to quarks Non-universal couplings to leptons Ingredients: Add an extra SU(2) factor to the SM gauge group Null or negligible couplings to electrons, as suggested by data Couplings to left-handed fermions, as suggested by b s and R(D(*)) apparent universal scaling An effective dynamical model in this direction [Greljo et al, 2015] 31

32 The model (I) Particle content Two scalar doublets: A bidoublet: SM fermions (f): charged universally under SU(2)2 VL fermions (F): charged universally under SU(2)1 SM-VL mixing 32

33 The issue of gauge mixing For unsuppressed z, gauge mixing effects are potentially of the same size as Z, W tree-level exchange (for certain observables) Z, W tree-level: Z, W tree-level + GM: Potential to spoil the desired couplings (Anomalous couplings to electrons, corrections to C9NP = - C10NP,...) Constrained by LEP at the per-mil level (Z- and W-pole observables) A second Higgs doublet Solution: free parameter 33

34 The model (II) 34

35 The model (II) Fermion representations Scalar representations self-dual bidoublet : 35

36 The model (II) Standard Yukawa terms VL mass terms MQ, ML : nvl x nvl matrices VL-SM Yukawa terms lq, ll : 3 x nvl matrices 36

37 The model (II) Scalar potential and symmetry breaking Doublets VEVs 37

38 The model (II) Particle spectrum I: Scalars 12 d.o.f. W, Z, W, Z long. components 6 d.o.f CP-even + CP-odd 1 + Charged 2 d.o.f. [ constrained 2HDM + CP-even singlet scenario ] Particle spectrum II: Fermions SM-VL mixing induced by lf 38

39 The model (II) Particle spectrum III: Gauge bosons Neutral gauge bosons controlled by vanishes for gauge mixing 39

40 The model (II) Particle spectrum III: Gauge bosons Charged gauge bosons controlled by vanishes for gauge mixing 40

41 The model (II) Z and W couplings to fermions Note: is the physical VL mass universal non-universal due to SM-VL mixing 41

42 The model (II) Z and W couplings to fermions Does not work! It works! 42

43 Our global fit Many more details in Boucenna, Celis, Fuentes-Martin, AV, Virto [arxiv: ] Bounds from Z and W pole observables [Efrati et al, 2015] Tests of lepton universality violation in tree-level charged current processes: and F = 1,2 transitions in the b s sector receiving NP contributions at tree-level Bounds from the lepton flavor violating decays and CKM inputs from a fit by the CKMfitter group with only tree-level processes 43

44 Our global fit Many more details in Boucenna, Celis, Fuentes-Martin, AV, Virto [arxiv: ] Free parameters: CKM matrix Global function gauge mixing Best-fit point: to be compared with In the parameter space region where RK and R(D(*)) are accommodated within 2σ, the Z and W bosons couple predominantly to the third fermion generation 44

45 Gauging the anomalies away Global fit EW precision data Flavor data The model gives a good fit to data Gauge-mixing must be suppressed. Otherwise R(D*) cannot be explained 45

46 More on gauge mixing Explaining the R(D*) best-fit requires a tiny GM parameter (otherwise too large NP contribution in other charged current processes) RK not very sensitive to GM effects (the required Z coupling is loop suppressed in the SM) 46

47 Predictions (1) Additional b c observables NP contributions have the same Dirac structure as the SM ones Enhancement in the R(Xc) inclusive ratio Global rescaling in the B D(*) t n decay rate. Differential distributions are SM-like. (2) Other RM observables RK, RK* and RΦ are strongly correlated (for example) 47

48 Predictions (3) Lepton flavor violation Z tree-level exchange can lead to observables LFV effects can be close to the experimental bound (4) LHC direct searches The Z boson will be produced at the LHC via Drell-Yan processes due to its couplings to the 2nd and 3rd generation quarks The usual limits (1st generation couplings) do not apply Nevertheless: the LHC is sensitive ATLAS search for a narrow t+ t- resonance excludes the light Z region (MZ < 1 TeV). Heavier Z bosons become broad and require dedicated searches 48

49 Summary 49

50 Summary The anomalies in B-meson decays constitute an intriguing set of hints for NP Possible NP explanations include charged Higgses, Z bosons, leptoquarks and some other possibilities, but finding a common explanation is not trivial A simple SU(2) gauge extension of the SM can do the job! 50

51 Summary The anomalies in B-meson decays constitute an intriguing set of hints for NP Possible NP explanations include charged Higgses, Z bosons, leptoquarks and some other possibilities, but finding a common explanation is not trivial A simple SU(2) gauge extension of the SM can do the job! Thank you! 51

52 Backup slides 52

53 The anomalies Episode : First anomalies found by LHCb Episode : Lepton universality violation [Hiller, Kruger, 2004] Episode : LHCb confirms first anomalies 53

54 Contributes to and [Bobeth et al, 2013] [CMS and LHCb, 2013] (at 1s) The model is compatible at 2s [Altmannshofer et al, 2014] Allowing for a 10% deviation from the SM expectation in the mixing amplitude 54

55 FlavorKit [Porod, Staub, AV, 2014] A computer tool that provides automatized analytical and numerical computation of flavor observables. It is based on SARAH, SPheno and FeynArts/FormCalc. Not limited to a single model: use it for the model of your choice Easily extendable Many observables ready to be computed in your favourite model! Manual: arxiv: Website: 55

56 Some comments on DM However: Higgs portal also possible Assumption: Z' portal Interplay between flavor and DM Favorable conditions (resonance) 56

57 Dark matter and LHCb anomalies (full) (dashed) (tree) (dotted gray) [ DM RD Computed with micromegas ] Parameters: Compatible with flavor constraints (small quark mixings) Resonance required to get the correct DM relic density Large loop effects for low 57

58 Loop corrections At 1-loop, the vector-like quarks contribute to all operators [ Computed with FlavorKit ] (full) (dotted gray) Non-negligible corrections to Unwanted contributions to other Wilson coefficients However: Valid region is safe 58

59 LFV in B meson decays What about LFV? [Glashow et al, 2014] Lepton universality violation generically implies lepton flavor violation Gauge basis Mass basis However: we must have a flavor theory in order to make predictions 59

60 Are the LHCb anomalies related to neutrino oscillations? Working hypothesis: What if? [Boucenna, Valle, AV, 2015] Neutrino oscillations Neutrinos B-physics LHCb sensitivity Lines: BF Bands: 60

61 Model classification Breaking pattern Source of non-universality L-BP : g-nu : Non-universal gauge couplings y-nu : Through non-universal mixings with other fermions Y-BP : L-BP g-nu No left-handed currents y-nu No GIM Y-BP Perturbativity 61

62 The diphoton excess (CP-odd state) and induced by loops of VL quarks and leptons required for flavor! Work in progress Can this model explain the LHC diphoton excess as well? 62

63 Other observables Explaining the R(D*) best-fit would induce a slight tension with the R(Xc) experimental measurement 63