1. Lepton Number and Lepton Flavour Violation
Search for Majorana neutrinos in B-decays ,
lepton flavour violation in - --+
and baryon number violation with LHCb  seen Paul Seifert's talk today
LHCb collaboration
54 institutions, 15 countries

2. Introduction Lepton Number Violation
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, (2012)
Such decays have previously been searched for:
- Ξ-pμ-μ- HyperCP
D. Rajaran et al. Phys. Rev. Lett. 94, (2005)
- Bhe+μ-, he+e+, he+μ+,hμ+μ+ h=π,K,ρ,K* CLEO
K.W. Edwards et al. Phys. Rev. D65, (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.

3. 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-+)+- -

4. B-Vertex Measurement B0 → J/Ψ (μ+μ-) K+ d~1cm s(t) ~40 fs B+ K μ+ μ-
Primary vertex
Proper-time resolution st = 40 fs
s(t) ~40 fs
B0 → J/Ψ (μ+μ-) K+
Vertex Locator (VELO)
Vertexing:
trigger on impact parameter
measurement of decay distance (time)

5. Momentum and Mass measurement : TrackerOT TT
LHCb IT
[LHCb-CONF ]
8276 signal TT
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: D p/p = 0.4–0.8% (2–100 GeV/c).
Bs  J/y f selection (J/y  m+m-, f  K+K-): s(mB) = 7 MeV/c2 (LHCb).
~ 20 MeV/c2 (ATLAS/CMS) yields/pb-1 and S/B lower.

6. Particle Identification
RICH: K/p identification using Cherenkov light emission angle
btag Bs K K
,K  Ds
Primary vertex
Bs → Ds K
KK : ± 0.06%
pK : 3.94 ± 0.02% 
RICH1: 5 cm aerogel n=1.03 , 4 m3 C4F10 n=1.0014
Pure sources of K and π given by D*+D0π+ , D0K-π+
RICH2: m3 CF4 n=1.0005

7. Particle identification: Calorimeters and L0 triggerh
ECAL (inner modules): σ(E)/E ~ 8.2% /√E + 0.9%
Calorimeter system :
Identify electrons, hadrons, π0 ,γ
Level 0 trigger: high ET electron and hadron

8. Muon identification 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 B+ K μ+ μ-
d~1cm
Primary vertex

9. Search for Lepton Number Violation at LHCb
Impressive limits to date from nuclear 0- decay on electrons: O(1025) years.
Yet heavy quark mesons could undergo the same process with muons: b d u c W- N - 
Phys. Rev. D 85, (2012) arXiv: v2
Virtual Majorana neutrino a)
Resonant neutrino production b)
Vub
Annihilation c)
New
Vcb
Also resonant production

10. Limits from B-factories
Belle results on B  D+l-l-
Based on 772106 BB events at (4s), collected with
the Belle detector at KEKB
BaBar results on B  h+l-l- with h=K,
Based on 471106 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

11. Analysis general aspects
Phys. Rev. Lett. 108, (2012)
Phys. Rev. D 85, (2012)
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
B-  J/ K- J/  +-
B-  (2s) K- (2s)  + - J/
Total efficiency + - K- : 0.99  0.01 %
Total efficiency + - + - K- :  %

12. Majorana neutrinos B-  +- -
K// misid rates from D* +D0(K-+)
K0s 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

13. Majorana neutrinos B-  D+(*)- -
Phys. Rev. D 85, (2012)
B-  D+- - , B-  D*+- -
Total efficiencies are  % and  %
D+ reconstructed via decay to K  , D*+ reconstructed via D0( K)
Any value of MN (virtual neutrinos)
6 evts 6.9  1.1 backg.
5 evts  1.0 backg.
Total systematics :
8.8 % (D+ ) , 8.2 % (D*+)
Dominated by branching ratios
of normalization channels and trigger efficiencies
Limits determined using
and taking the vaue in which such probability is (95 % C.L.)

14. Mass and lifetime acceptance for on-shell Majorana neutrinos
Finite neutrino lifetimes ignored so far (except for off-shell production)
Sensitivity is lost for lifetimes longer than 10-10s to 10-11s.
B-  +--
B-  Ds+--
B-  D0 +--
Mass resolution
Neutrino mass acceptance

15. Systematic uncertainties for B-  DX--

16. Systematic uncertainties for B-  +- -

17. B-  Ds+- - and B-  D0 +- -
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-)
B-  D0+- -
D0 reconstructed via
decay to K
MN spectra consistent
with polynomial backgs.
estimated from sidebands MN
Phys. Rev. D 85, (2012)

18. Mass-dependent Majorana neutrino limits
B-  +- -
B-  Ds+- -
B-  D0+- -
Upper limits (95% C.L.) are set at
each MN mass by searching a signal
within  3N in small steps.
Phys. Rev. D 85, (2012)
For B-  D+(*)- - , limits
on the coupling require calculation
of hadronic form factor
(as for 0 decay) .
A model dependent calculation2
was used for B-  D0 +-- , but
the mode +-- is more sensitive.
2 D. Delepine, G. Lopez Castro, and N. Quintero, Phys. Rev. D84 (2011) , arXiv:

19. Limits on Majorana coupling |V4 |
Phys. Rev. D 85, (2012)
B-  +--
B  
LHCb
Mass dependent upper limits
on the coupling |V4 | 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:

20. Summary on LNV in B decays
a BaBar,Phys. Rev. D 85, (2012)
b CLEO, Phys. Rev. D 65, (2002)
c Belle, Phys. Rev. D 84, (R), (2011)
d LHCb, CERN-PH-EP , arXiv: (2012)
e LHCb, Phys. Rev. Lett (2012)

21. Summary of LNV and LFV at LHCb
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
|V4| of a 4th generation N to W, using B  
LHCb is approaching B factories for  
 first measurement at hadron colliders: < 7.8 × % C.L.
LHCb has set limits ( 10-7) for the first time on  (B –L) = 0
decays - p̅-+ and - p--
Only up to 1.0 fb-1 used by LHCb, currently 3.0 fb-1 on tape

22. THANKS

23. Limits from B factories