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Recent LHCb results on rare decays

ICNFP 2014 Kolymbari, Greece

Sajan Easo04-08-2014

On behalf of the LHCb collaboration

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Outline

Introduction to LHCb : Talk on Friday by D. M. Santos Saturday by M.Kreps

Indirect searches for New Physics

Beauty rare decays

Charm rare decays

Summary

• Leptonic decays• Electroweak penguin decays

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LHCb Experiment

Forward spectrometer : 2 < h < 5

b 13.0)5.4(75.3X)bbpp acc

b65(frag)) 116(syst)12(stat)(1419X)cc(pp acc

Phys.Lett. B 694 (2010) 209 -216

Nucl. Phys. B 871 (2013)1-20

Vertex resolution: sx ~ 16 mm, sy~16 mm sz ~76 mm for 25 tracksTracking : Dp/p = 0.35 -0.55 % RICH : PID in 1-100 GeV/c Muon system :

ECAL : (E in GeV)

HCAL : (E in GeV)

Bs Mass resolution = 6 MeV/c2 in

5%~K)( misIDfor 95% ~ K)K(

3%-1)( misIDfor %97~)(

%1%10

~E

E

E

%10%70

~E

E

E

KKJ/Bs

JINST 3 (2008) S08005

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LHCb: Trigger and Offline selections

2011 : 1 fb-1 of data at 7 TeV2012 : 2 fb-1 of data at 8 TeV

Level 0 : Hardware Trigger

HLT : Software Trigger

Offline Selection:

One of the Multivariate classifiers:

• Largest PT (ET) of hadron/e/g/m Muon PT> 1.76 GeV, Hadron ET> 3.7 GeV

e/g ET > 3.5 GeV

• Stage 1 : Selection based on IP, PT

• Stage 2 : Full event reconstruction mass cuts, Multivariate selection (MVA)

• Cuts based on Event topology P,PT of tracks, vertex quality, IP etc.• Use PID information• Multivariate selections (MVA)

• Boosted Decision Tree (BDT)

JINST 8 (2013) P04022

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Measure FCNC transitions, where NP is likely to emerge Example: OPE expansion for b s transitions

NP may modify ,add new operators

Misiak: Nucl. Phys B393 (1993) 23-25Buras : arXiv: hep-ph: 9806471 (1998)

i

SMin suppressed

ii ii

*tstb

Feff ])(O)(C)()O(C[ VV

2

G4H

parthandedrightparthandedleft

iC iO

Indirect searches for New Physics (NP)

Precision measurements: Discover “virtual” new particles in loop processes

i = 1,2 Tree = 3-6,8 Gluon penguin = 7 Photon penguin = 9,10 Electroweak penguin = S Higgs (scalar)penguin= P Pseudoscalar penguin

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Suppressed by FCNC and helicity SM prediction

Decay SM

sB -910 23.065.3 0B -1010 0.11.1

Bobeth et.al PRL 112 101801 (2014)

4A

6

m

tan )(

sBB

MSSM (with R-Parity conservation)

Ratio is a test of the minimal flavour violation hypothesis

Eur. Phys. J C72 (2012) 2172

00s B and B

)B ( 0 B is suppressed by a factor compared to that of Bs

2tstd | V / V |

Relative uncertainties in SM for Bsm+m-

00s B / B

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B0

Bs0

00s B and B

• BDT trained on MC and calibrated using real data• Control channels:

• Branching fraction normalized with respect to the control channels.

• Simultaneous unbinned maximum-likelihood fit to determine the branching fractions for the two channels.

• Mass plot here with BDT > 0.7, for illustration.Red: Bs

0

Green : B0

J/ B , KB , K J/B 0s

0

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In 3 fb-1 , LHCb sees evidence at 4 s level for and at 2 s level for the B0 channels.

-93.01.11.00.1

0s 10 )9.2()B(

B

PRL 111 (2013) 101805

Preliminary combination of CMS+LHCb yields

Observation at more than 5 s

All consistent with SM expectations. In CMSSM regions with large tan (>50) b excluded (in m0 , m1/2 plane: 0-2TeV range) Work in progress to combine CMS+LHCb results in a more sophisticated way.

00s B and B

-106.04.24.01.2

0 10 )7.3()B(

B0sB

PRL 112 (2014) 101801

F.N.Mahmoudi, arXiv:1310.2556

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Photon polarization in b s g decays

First penguin decay ever observed : *00 KB CLEO in 1992

PRL 71 (1993) 674

B-factories: Inclusive and exclusive branching fractions are compatible with SM expectations.

Yet untested: photon polarization in b s gIn SM : photons are predominantly left-handed due to charged current interaction ) m/m ~ C/C ( bs77

One of the ways of testing 77 C/C

Gronau & Pirjol PRD 66 (2002) 054008 KK)1270(K 1where

)1270(K B 1as such decays Use

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Conceptually similar to the Wu experiment in 1956 which observed parity violation.

In LHCb , we reconstruct the decay

KB Infer photon polarization from the up-down asymmetry of the photon direction in the K+ p+ p- rest-frame. Unpolarized photons would have no asymmetry.

Photon polarization in b s g decays

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Reconstruction of KB Selection using BDT ~ 13000 signal candidates in 3 fb-1 Several overlapping resonances in m (K+ p+ p-) Data divided in to 4 bins in m (K+ p+ p-)

Up-down asymmetry :

K1(1270), K1(1400), K2*(1430), K2(1580),K2(1770),K3*(1780)

Photon polarization in b s g decays

PRL 112 (2014)1161801

red solid:signalcomb.background: green dottedmissing pion background: black dottedother partially reconstructed background: purple dash-dotted

Bin boundaries: 1.1-1.3-1.4-1.6-1.9 GeV/c

PRL 112 (2014)1161801

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Best Fit in Blue, Fit with no photon polarization in red (C’27 - C2

7)/(C’27 + C2

7)=0

Photon polarization in b s g decays

PRL 112 (2014)1161801

13

Combining the 4 bins the photon is observed to be polarized at 5.2 s level .

This is the first observation of photon polarization in bs g decays

In order to determine if the polarization is as expected in SM, further input from theory is needed.

PRL 112 (2014)1161801

% 1.94.5- %, 1.85.6

%, 2.04.9 %, 1.7 6.9 Aud

Photon polarization in b s g decays

4s 2.5s 3.1s 2.4s

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Electroweak penguins : b → ll s

Standard Model (SM)

New physics (NP) : Loop order and tree level

Sensitivity to the different SM and NP contributions from decay rates, angular observables and CP asymmetries

Long Distance effects : , can be removed with mass cuts ll)c(c , sccb__

)(q 22 llm

S.Jäger

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*0 K B Angular distribution:

)(q 22 m

AFB : Dimuon forward-backward asymmetryFL : Fraction of longitudinal K*0 polarisationS3 : Transverse asymmetry (sensitive to virtual photon polarization)A9 : A CP Asymmetry (ACP)

11 terms reduced to 7 terms usingangular folding : f + f p if f <0

LHCb measured these parameters and the branching fraction as a function of q2

f

]2sin sinsin A cos sin A3

4 2 cos sin sin S

)1cos 2(sin)F 1(4

1 ) 1- cos 2(cos F

sin )F1(4

3cosF[

16

9

dq d cos d cos d

d

)/dq(d

1

229

2FB

223

22L

22L

2L

2L2

K

4

2

lKlKlK

lKlK

KKl

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b → ll s Differential branching fraction

LHCb reconstructed

Modes with are experimentally challenging due to its long lifetime.

Signals reconstructed for all these modes with 3 fb-1 of data. For the , results from 1 fb-1 of data quoted, for now.

Branching fractions normalized to those of the corresponding

)K (Kor )K(K

), ( K ,Keither asKaon *00

s*

-0s

0sK

(*)K J/ B

*00 KB

events 814746 : K B

events 17 176 : B

0

0sK

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Differential branching fraction b → ll s

JHEP 06 (2014) 133

JHEP 1308 (2013) 131

*00 KB

*00 KB with 1 fb-1 of data, all others with 3 fb-1 of data

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0*0 K B

JHEP 1308 (2013) 131 using 1 fb-1 of data

0*0 K B LHCb measurements:

All in agreement with SM

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*0 K B

ACP using 3 fb-1 of dataLHCb-Paper-2014-032

) K B (A *00 CP prelim.

In agreement with SM. Most precise measurement to date.

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*0 K B LHCb also measured which are largely free from form-factor uncertainties Descotes-Genon et.al. JHEP,1305:137,2013)F1(F

S P

LL

4,5'4,5

In the 1 fb-1 of data, LHCb observes a local discrepancy of 3.7 s in P5’ (Probability that one bin varies by this this much (look-elsewhere effect) is 0.5 % ).

PRL 111 (2013) 191801

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*0 K B Interpreting the anomaly in P5’ : At least 28 theory papers so far.

Descotes-Genon, Matia, Vitro:

Fit this and other measurements to get a 4.5 s discrepancy with SM. They favour a modified C9

NP = -1.5 (Non-SM vector current )

Altmannshofer & Straub : [ EPJC 73 (2013) 2646 ]

Perform a global analysis and find discrepancies at the level of 3 s. Data best described by a modified C9 and C9’ and introducing a flavour changing Z’ boson at O(1 TeV)

Gauld, Goertz & Haish: [ JHEP 01 (2014) 069 ]

Also prefer Z’ but with mass O(7 TeV)

Beaujean, Bobeth &van Dyk : [ arXIV:1310.2478 ]

Float form factor uncertainties as nuisance parameters and find the discrepancy can be reduced to 2s.

[ PRD 88 (2013) 074002 ]

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*0 K B

Further verification needed with more data and channels -Some of the models expect suppression of B ( ) K B *0

Jaeger & Camalich : JHEP 05 (2013) 043

Also explore the size of the form factor uncertainties in the low q2 region and gets a reduced discrepancy

J.Lyon & R.Zwicky : arXiv:1406.0566

Explore the QCD effects related to the interference pattern of various charm resonances in the . They perform a combined fit to the BESII data on and the LHCb data. They claim that these charm resonance effects can accomodate the discrepancy.

hadrons ee

KB

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Test of Lepton Universality

In the SM, dominant processes couple with equal strengths to all leptons.

Test this using

Reconstruction of is experimentally challenging due to bremsstrahlung emission from . The effect from this is corrected using photons detected in the calorimeter, with ET > 75 MeV.

-eeK B and K B

in SM

JHEP 12 (2007) 040

-eeK B e

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K )ee ( J/ B - -eeKB

CandidatesTriggered by e

e, whereK ) (J/ B - lll

Measurement in the 1<q2<6 GeV2/c4 region:

Away from the resonant decays Avoid region above the Y(2S) where broad charmonium resonances decay to l+l-

Migration of events into and out of this region corrected using simulations

K ) ( J/ B -ll

Ratio of the relative branching fractions with respect to cancels potential sources of systematic uncertainties.

Test of Lepton Universality

Dark shaded:combinatorial backgroundLight shaded: partially reconstructed b-hadron decays

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This differs from SM at 2.6 s level This is using the 3 fb-1 of data This is the most precise measurement of RK to date.

LHCb: arXIv:1406.6482Belle: PRL 103 (2009) 171801BaBar : PRD 86 (2012) 032012

At least one of the models with Z’ predicts a suppression of the BF for

-eeK Bfor that tocompared

K B

LHCb plans make the same measurement in other similar channels and also plans to use more data in the coming years.

Test of Lepton Universality

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Charm Decays

In SM, in D-decays, FCNC at loop level is suppressed by GIM mechanism more effectively than in B-decays . ( no top quark in the loop)

Typical branching fractions of c u m+ m- in the range (1 -3 ) X 10 -9

This allows for search for BSM physics in D-decays . Example:

D

22 GeV m

27Backgrounds from sD and D

Green: best fit to (s)D

Charm Decays )(D sLHCb Search for

• Using 1 fb-1 of data

PLB 724 (2013) 203-212

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Charm Decays

Use the CLs method to find the upper limits:

Each of these limits is an improvement over the existing limits , by a factor of 50 Existing limits from D0 and FOCUS : Phys. Rev. Lett. 100 (2008) 101801 , Phys. Lett B572 (2003) 21

For lepton number violating decays: existing limits from BaBar, LHCb: Phys.Rev D84 (2011) 072006, arXiv 1201.5600

PLB 724 (2013) 203-212

90% (95%) CL limits

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Charm Decays LHCb used 1 fb-1 of data from 2011 to search for D0 selected in Data divided into 4 ranges of m(m+m-)

0D

Low m(m+m-) /r w

High m(m+m-)

0* DD

Signal region

Signal region

PLB 728 (2014) 234-243

f

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Charm Decays PLB 728 (2014) 234-243

SM predictions of order (10 -9 ) LHCb improves the limits by a factor of 50 , over the previous limits Previous limits from E791: Phys. Rev.Lett. 86 (2001) 3969

0D

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Summary

LHCb has published several results on the search for New Physics from the data collected in 2011-12.

The discrepancy with SM observed in the BK* mm has generated lots of interest in from theory colleagues.

The test of lepton universality produces a deviation from SM at 2.6 s level, which is starting to be interesting.

In the coming 3 years we expect to collect 5 fb-1 of data . From 2018 onwards with LHCb upgrade we would get 5 fb-1 of data per year. These would enable LHCb to increase its sensitivity to New Physics.

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Backup Slides

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b → ll s

events 16162KB

events 562361 :KB*

*00

:

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Event Selection :

Branching Fraction: Normalized after similar event selection in B+ J/y K+ , B K p

Search for B (s) m + m -

BDT , trained on MC and calibrated using real data

Signal : B h+ h- (h= K or )p

Background : Bs mass sidebands

norm

sig

s

normnorm norm N

Nf

f

sigBB

020.0017.0017.0253.0/ ds ff

PRL 107(2011)211801LHCb:A control channel

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Charm Decays

Similar search in 4-body decays 0D

Lepton number violating decay:

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P5’ Discrepancy

J.Lyon, R.Zwicky : arXiv:1406.0566

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Charm Decays Upper limits estimated using the CLs method, for the

0D

SM predictions of order 10 -9 . Hence these results are compatible with SM. Current limits improves the previous limits by a factor of 50 . Previous limits from E791: arXiv:hep-ex:0011077

PLB 728 (2014) 234-243

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B0s

Constraints on CMSSM

Black line: Direct search limits from ATALS SUSY searches with 20 .3 fb-1

White line: Where the Higgs mass can reach a value of 122GeV

F.N.Mahmoudi, arXiv:1310.2556

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Search for Majorana neutrinos in B

Lepton Number Violating channel : search for majorana neutrino masses in the range between 250 and 5000 MeV and lifetimes 0-1000 ps.

Phys. Rev. Lett. 112 (2014) 131802

-9- 10 4.0 ) B ( B At 95 % C.L.

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Search for p and

Phys. Lett. B724 (2013) 36-45

About 70% t from sD

Expected limits at 90 %(95% ) CL

Observed limits at 90% (95%) CL