B. Adeva, University of Santiago de Compostela 3rd Workshop Flavour Physics LHC era Valencia 6th February, 2013 1

Search for Majorana neutrinos in B-decays ,lepton flavour violation in - --+ and baryon number violation with LHCb seen Paul Seifert's talk today

Lepton Number and Lepton Flavour Violation

54 institutions, 15 countries

LHCb collaboration

B. Adeva, University of Santiago de Compostela 3rd Workshop Flavour Physics LHC era Valencia 6th February, 2013

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No known symmetry associated with Lepton Number Conservation. Gauge symmetry is behind electric charge conservation.

New Physics models such as those with Majorana neutrinos, or LR symmetric models with doubly charged Higgs boson can violate LN conservation. LHCb has searched for B- +- - and B- K+- - Phys. Rev. Lett. 108, 101601 (2012)

Such decays have previously been searched for: - Ξ-pμ-μ- HyperCP D. Rajaran et al. Phys. Rev. Lett. 94, 181801 (2005)

- Bhe+μ-, he+e+, he+μ+,hμ+μ+ h=π,K,ρ,K* CLEO K.W. Edwards et al. Phys. Rev. D65, 111102 (2002)

- 0νββ excellent review: J. J. Gomez-Cadenas et al. Riv. Nuovo Cimento 35, 29 (2012)

- pp (e+e+,e+μ+,μ+μ+) + X , high mass SS dileptons ATLAS G. Aad et al. J. High Energy Phys. 10 (2011) 107.

Introduction Lepton Number Violation

LHCb detector overview and performance

Search for B- +- - , B- K+- - , B- Ds+( ϕ(K+K-)π+ )--

B- D+(K-+π+)-- , B- D*+(D0+)- - , B- D0(K-+)+- -

B-Vertex Measurement

Vertex Locator (VELO)Vertexing:• trigger on impact parameter• measurement of decay distance (time)

B+

K

μ+

μ-

d~1cmPrimary vertex

Proper-time resolution t t = 40 fs

) ~40 fs

B0 → J/Ψ (μ+μ-) K+

• TT and Inner Tracker: silicon micro-strips ~ 200 μm pitch. 12 m2 of silicon 4 layers with (0º, +5º,5º, 0º) stereo angle.

• Outer Tracker: drift chamber with 5 mm diameter straws gas Ar/CO2/O2 (70:28.5:1.5).

Resolution: p/pp/p = 0.4–0.8% (2–100 GeV/c)= 0.4–0.8% (2–100 GeV/c).

Bs J/ selection (J/KK (m(mBB) = 7 MeV) = 7 MeV/c/c22 (LHCb). (LHCb).

~ 20 MeV/c2 (ATLAS/CMS) yields/pb-1 and S/B lower.

OT

ITTT

TT

[LHC

b-C

ON

F-20

11-0

49]

8276 signal

LHCb

Momentum and Mass measurement : Tracker

btag

Bs K

K

,K

Ds

Primary vertex

RICH2: 100 m3 CF4 n=1.0005

RICH: K/ identification using Cherenkov light emission angle

RICH1: 5 cm aerogel n=1.03 , 4 m3 C4F10 n=1.0014

Pure sources of K and π given by D*+D0π+ , D0K-π+

KK : 96.77 ± 0.06%K : 3.94 ± 0.02%

Bs → Ds K

Particle Identification

e

h

Calorimeter system : • Identify electrons, hadrons, π0 ,γ• Level 0 trigger: high ET electron and hadron

ECAL (inner modules): σ(E)/E ~ 8.2% /√E + 0.9%

Particle identification: Calorimeters and L0 trigger

Muon system: •Level 0 trigger: High Pt muons•pure muon sample from J/Ψ μ+μ- μ-ID requirement applied to only one

Primary vertex

B+K

μ+

μ-

d~1cm

Muon identification and L0 trigger

B. Adeva, University of Santiago de Compostela 3rd Workshop Flavour Physics LHC era Valencia 6th February, 2013

Phys. Rev. D 85, 11204 (2012) arXiv:1201.5600v2 b

du

c

¯

W-

W-

N

-

-

a)

b)

c)

Virtual Majorana neutrino

Resonant neutrino production

Also resonant production

Impressive limits to date from nuclear 0- decay on electrons: O(1025) years.Yet heavy quark mesons could undergo the same process with muons:

Vcb

Vub

Annihilation

New

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Search for Lepton Number Violation at LHCb

B. Adeva, University of Santiago de Compostela 3rd Workshop Flavour Physics LHC era Valencia 6th February, 2013

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Belle results on B D+l-l- Based on 772106 BB events at (4s), collected withthe Belle detector at KEKB

BaBar results on B h+l-l- with h=K, Based on 471106 BB events at (4s), collected with

the BaBar detector at SLAC Event selection similar to other B analysis. B mass and energy

calculated in center of mass system using Ebeam constraint

Limits from B-factories

B. Adeva, University of Santiago de Compostela 3rd Workshop Flavour Physics LHC era Valencia 6th February, 2013 11

Search for the decays B- +- - , B- Ds

+- - , B- D+- - , B- D*+- - , B- D0+- -

using 0.41 fb-1 Neutrinos are assumed to have a very narrow width compared to detector resolution.

Limits calculated asuming phase space, and also as function of neutrino mass Signal yields are normalised to B channels with known branching fractions with

the same number of muons in 3-body and 5-body final states

Phys. Rev. D 85, 112004 (2012)

B- J/ K- J/ +- B- (2s) K- (2s) + - J/

Total efficiency + - K- : 0.99 0.01 % Total efficiency + - + - K- : 0.078 0.002 %

Analysis general aspects Phys. Rev. Lett. 108, 101601 (2012)

B. Adeva, University of Santiago de Compostela 3rd Workshop Flavour Physics LHC era Valencia 6th February, 2013 12

B- +- -

K// misid rates from D* +D0(K-+) K0

s and J/ Peaking background from misid

B- J/ K- and B- J/- (2.5 evts) Combinatorial background from

fit to the sidebands (5.3 evts) Many systematics cancel in ratio to

normalisation channel

Majorana neutrinos B- +- -

B. Adeva, University of Santiago de Compostela 3rd Workshop Flavour Physics LHC era Valencia 6th February, 2013 13

B- D+- - , B- D*+- -

Total efficiencies are 0.099 0.007 % and 0.066 0.005 % D+ reconstructed via decay to K , D*+ reconstructed via D0( K) Any value of MN (virtual neutrinos)

Phys. Rev. D 85, 112004 (2012)

Limits determined using

and taking the vaue in which such probability is 0.05 (95 % C.L.)

obsNN

B)(SN

obs N!

eB)(S)NP(N

Total systematics : 8.8 % (D+ ) , 8.2 % (D*+)Dominated by branching ratios of normalization channels and trigger efficiencies

6 evts 6.9 1.1 backg. 5 evts 5.9 1.0 backg.

Majorana neutrinos B- D+(*)- -

B. Adeva, University of Santiago de Compostela 3rd Workshop Flavour Physics LHC era Valencia 6th February, 2013

B- +-- B- Ds+-- B- D0 +--

Finite neutrino lifetimes ignored so far (except for off-shell production)Sensitivity is lost for lifetimes longer than 10-10s to 10-11s.

Neutrino mass acceptanceMass resolution

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Mass and lifetime acceptance for on-shell Majorana neutrinos

B. Adeva, University of Santiago de Compostela 3rd Workshop Flavour Physics LHC era Valencia 6th February, 2013

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Systematic uncertainties for B- DX--

B. Adeva, University of Santiago de Compostela 3rd Workshop Flavour Physics LHC era Valencia 6th February, 2013

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Systematic uncertainties for B- +- -

B. Adeva, University of Santiago de Compostela 3rd Workshop Flavour Physics LHC era Valencia 6th February, 2013 17

B- Ds+- -

Ds reconstructed via decay to KK

Heavy neutrino can decay to Ds

+-

Ds+ decay tracks form a

vertex with - candidate then a detached vertex with second - (B-)

Phys. Rev. D 85, 112004 (2012)

B- D0+- -

D0 reconstructed via decay to K

MN spectra consistent with polynomial backgs. estimated from sidebands

MN

B- Ds+- - and B- D0 +- -

B. Adeva, University of Santiago de Compostela 3rd Workshop Flavour Physics LHC era Valencia 6th February, 2013

2 D. Delepine, G. Lopez Castro, and N. Quintero, Phys. Rev. D84 (2011) 096011, arXiv:1108.6009.

A model dependent calculation2

was used for B- D0 +-- , but the mode +-- is more sensitive.

For B- D+(*)- - , limits on the coupling require calculation of hadronic form factor (as for 0 decay) .

Phys. Rev. D 85, 112004 (2012)

B- +- - B- Ds+- - B- D0+- -

Upper limits (95% C.L.) are set at each MN mass by searching a signal within 3N in small steps.

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Mass-dependent Majorana neutrino limits

B. Adeva, University of Santiago de Compostela 3rd Workshop Flavour Physics LHC era Valencia 6th February, 2013

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B LHCb

B- +--

Mass dependent upper limits on the coupling |V4 | of a 4th generation Majorana neutrino to a muon and virtual W 1.

1 A. Atre, T. Han, S. Pascoli, and B. Zhang, JHEP 05 (2009) 030, arXiv:0901.3589.

Phys. Rev. D 85, 112004 (2012)

Limits on Majorana coupling |V4 |

B. Adeva, University of Santiago de Compostela 3rd Workshop Flavour Physics LHC era Valencia 6th February, 2013 20

a BaBar,Phys. Rev. D 85, 071103 (2012)b CLEO, Phys. Rev. D 65, 111102 (2002)c Belle, Phys. Rev. D 84, 071106(R), (2011)d LHCb, CERN-PH-EP-2012-006, arXiv:1201.5600 (2012)e LHCb, Phys. Rev. Lett. 108 101601 (2012)

Summary on LNV in B decays

B. Adeva, University of Santiago de Compostela 3rd Workshop Flavour Physics LHC era Valencia 6th February, 2013 21

neither lepton number violation nor lepton flavour violations observed yet

heavy quark and lepton decays provide good probes for Lepton Number & Flavour Violation. Excellent sensitivity achieved at B factories.

LHCb extends knowledge on forbbiden B decays in LNV processes to 10-6…-8 , establishing best limits on the coupling |V4| of a 4th generation N to W, using B

LHCb is approaching B factories for first measurement at hadron colliders: < 7.8 × 10-8 95% C.L.

LHCb has set limits ( 10-7) for the first time on (B –L) = 0 decays - pY -+ and - p--

Only up to 1.0 fb-1 used by LHCb, currently 3.0 fb-1 on tape

Summary of LNV and LFV at LHCb

B. Adeva, University of Santiago de Compostela 3rd Workshop Flavour Physics LHC era Valencia 6th February, 2013

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THANKS

B. Adeva, University of Santiago de Compostela 3rd Workshop Flavour Physics LHC era Valencia 6th February, 2013

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Limits from B factories