Search for New Physics with the LHCb Detector

1
Search for New Physics with the LHCb Detector
Niels Tuning NIKHEF/ Free University
Amsterdam On behalf of the LHCb
collaboration MIAMI2005, December 15th 2005
2
Outline

• Lets consider a GUT scenario and show the
  possibilities for the LHCb experiment

• GUT Neutrino mixing
• Predictions for b?s
• Signatures in LHCb
• LHCb signatures
• The Box Diagram
• Bs mixing Bs?Ds-p
• CP phase Bs?J/?f
• The Penguin Diagram/Rare Decay
• Rare decays B(s)?(K)µµ

3
Grand Unified Theories

• Can the large neutrino mixing angles be
  transferred to the hadronic sector?
• GUT unifies quarks and leptons

• Simplest GUT SU(5)
• Down type quarks with leptons in mulitplet

4
To SUSY or not to SUSY

• SUSY GUT vs non-SUSY GUT
• Unification 3s vs 12s
• Scale 3.1016 vs 1015 GeV
• t p decay MGUT4
• R-parity in SUSY can prevent unwanted baryon
  number violation
• sin2?W from SUSY in better agreement with data

Phys.Lett.B592(1),2004
5
The model SUSY SO(10)

• Why SO(10) ??
• Small extension of SU(5)
• SO(10) ? SU(5) x U(1)
• 16 10 ?5 1
• It nicely incorporates the right-handed ?
• The see-saw mechanism explains small non-zero
  neutrino mass, and even relates M?R?MGUT

• It relates neutrino mixing to squark mixing!

Chang, Masiero, Murayama Phys.Rev.D67 (075013),
2003, hep-ph/0205111
Barbieri, Hall Phys.Lett.B338(212),1994,
hep-ph/9408406
Jager, Nierste Eur.Phys.J.C33(256),2004 hep-ph/031
2145
Harnik,Larson,Murayama,Pierce Phys.Rev.D69(094024)
,2004 hep-ph/0212180
6
The model SUSY SO(10)

• Superpotential (16 are fermions, 10 Higgses)

Chang, Masiero, Murayama Phys.Rev.D67 (075013),
2003, hep-ph/0205111

• YU contains the large top coupling
• YU can be symmetric. In Yu diagonal basis we have

Just as in the SM, we rotate the d-quarks

• Break to SU(5)
• Break to MSSM (rh ?)

Without neutrino mass, UMNS could be rotated away
7
Neutrino mixing Super Kamiokande
?µ??t
L/E (km/GeV)
Phys.Rev.Lett.81 (1562),1998, hep-ex/9807003
Phys.Rev.D71112005,2005, hep-ex/0501064
?m22.2 10-3 eV2, sin2?231
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Neutrino mixing ? squark smixing

• Consequences
• No effect in sR?bR (i.e. CKM), because there is
  no right handed coupling
• Observable effects in mixing between s?b
• The Box Diagram
• Bs mixing Bs?Ds-p
• CP phase Bs?J/?f LHCb
• The Penguin Diagram/Rare decay
• Rare decays B(s)?(K)µµ-

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Size of the Box Bs mixing (?ms)
New particles can affect the Box
?msSM ? Vts2
?ms ? VtsVNP2

• Remember B0d oscillations
• Predicted heavy particle
• ? mtopgt50 GeV
• Needed to break GIM cancellations

?
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Phase of the Box Bs?J/?f

• ?ms is senstive to A(B0??B0)
• We can also probe the phase of A(B0??B0)
• Interference of two diagrams

Ball et al,Phys.Rev.D69(115011),2004 hep-ph/031136
1

• B0s?J/?f Golden decay
• Theoretically clean
• sinfs -A??4/A?2 -2??2 ? -0.03
• Any larger asymmetry means new physics
• New physics appears in the box, as before

B0s?J/?f
?
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Rare decays B(s)?(K)µµ-

• s?b also appears in Penguin Diagram
• Affects rare decay B0?Kµµ-

• Similarly, Bs?µµ- is very promising
• SO(10) unifies fermion masses, and predicts
• ? tan ß mt(MZ)/mb(MZ) 40-50

The smoking gun of SO(10) Yukawa unification...
Blazek,Dermisek,Raby Phys.Rev.D65(115004),2002 hep
-ph/0201081
Dedes,Dreiner,Nierste Phys.Rev.Lett.87(251804),200
1 hep-ph/0108037
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Neutrino mixing ? squark smixing

• Consequences
• No effect in sR?bR (i.e. CKM), because there is
  no right handed coupling
• Observable effects in mixing between s?b
• The Box Diagram
• Bs mixing Bs?Ds-p
• CP phase Bs?J/?f LHCb
• The Penguin Diagram/Rare decay
• Rare decays B(s)?(K)µµ-

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What is LHCb?

• pp with ?s 14 TeV
• L 2.1032 cm-2s-1
• 1012 b-hadrons per year
• Start in July 2007

10 meter
20 meter

• Aim
• measure CP violation and rare decays
• Bs mixing
• CKM angles a, ß, ?
• Small branching fractions

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Status
LHC accelerator
LHCb experiment
Magnet
RICH
Muon Filter
LHC tunnel
LHC dipole
Cryogenic servicesline
1 December 2005
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LHCb spectrometer
VELO Vertex Locator TT, T1, T2, T3
Tracking stations RICH1-2 Ring
Imaging Cherenkov detectors ECAL, HCAL
Calorimeters M1M5 Muon stations
collision point
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Why LHCb?

• High cross section
• LHC energy
• Large acceptance
• bs produced forward
• Trigger
• ? Low pT
• Leptonshadrons
• Particle identification with RICH

Tevatron LHCb ATLAS/CMS
vs (TeV) 2 14 14
s(pp? bb)(µb) 100 500 500
L (cm-2s-1) 2008 4.1031 2.1032 1033
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Bs mixing, ?ms in LHCb

• Measure B0s?B0s
• Need to know how B0s was produced flavour
  tagging
• Need to know how B0s decayed use Bs?Ds-p

Bs?Ds-p (tagged as Bs)
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Bs mixing, ?ms in LHCb
Bs?Ds-? proper time resolution ?t  40 fs

• Measurement of ?ms is one of the first physics
  goals
• Expect 80k Bs ? Ds-p events per year (2 fb1)
• Excellent proper time resolution is vital
• Average ?t  40 fs
• 5s observation for ?ms20 ps-1
• Tevatron 6 fb1 all years?
• ATLAS/CMS 30 fb1 3 years
• LHCb 1/4 fb1 2 months

• Standard Model 20 ps-1 UT
  fit
• Present experimental limit gt14.5 ps-1
  Tevatron
• 5s observation in 1 year lt68 ps-1 LHCb
  

Prediction for ?ms from UT fit
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Phase Bs?J/?f in LHCb
Dunietz et al, Phys.Rev.D63(114015),2001 hep-ph/00
12219
A? CP odd A0, CP even

• B0s?J/?f
• Theoretically clean and experimentally easy
• J/??µµ trigger
• J/?(µµ)f(KK) 4 charged tracks
• Annual yield 120k events, S/B3
• But need angular analysis
• Final state contains a mixture of CP-odd and
  CP-even
• Fit for sin fs, DGs and CP-odd fraction
• (needs external ?ms)

Bs?J/?f (Bs tagged)
? Proper time t (ps)
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Rare Decays B(s)?(K)µµ- in LHCb
Thesis P.Koppenburg
Hurth, Rev.Mod.Phys.75(1159), 2003. hep-ph/0212304

• B0?Kµµ-
• Annual yield 4400 events, S/B3
• BR(B?Kµµ- )1.2 10-6
• Sign for new physics FB-asymmetry

Theory
LHCb

• Bs?µµ-
• Maybe LHCb first hot result!
• BR(Bs?µµ- )3 10-9 30 evts/year
• Background estimate difficult
• Generate 107 (b?µ, b?µ)-events
• 0 events pass selection
• But in 1 year we have 1010 (b?µ, b?µ)

(mµµ/mB)2
(mµµ)2
LHCb Bs?µµ- mass resolution
CDFD0 R.Bernhard et al hep-ex/0508058
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So, what do we have

• Bs ? Ds-p
• Additional contribution in box diagram
• 80k events per year
• proper time resolution is excellent ?t  40 fs
• Bs?J/?f
• Additional phase in box diagram
• 120k events per year
• Theoretically clean and experimentally easy
• B0?Kµµ-
• Annual yield 4400 events, S/B3
• Sign for new physics FB-asymmetry
• Bs?µµ-
• Annual yield 30 evts/year
• Very sensitive to new physics

• CP CKM angles
• angle ? (Bs?DsK, B?D0K, B(s)?pp/KK)
• angle a (B?ppp)
• angle ß (B?J/?Ks B?fKs,)
• BR(B?K?), Bc, ,

Many other things
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Summary

• Neutrino mixing, combined with SO(10) GUT,
  predicts visible effects in LHCb
• The Box Diagram
• Bs mixing Bs?Ds-p
• CP phase Bs?J/?f
• The Penguin Diagram/Rare Decay
• Rare decays B(s)?(K)µµ

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Backup Slides
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b?s?

• Experimental constraints
• BR(b?s?)SM (3.60.3) 10-4
• BR(b?s?)exp (3.30.3) 10-4
• BR(B?K?)exp (4.010.20) 10-5

• It is possible to increase ?ms, given BR(b?s?)
• Example mg200 GeV, mR31200 GeV
• BR(b?s?) 16
• ?ms 30 ps-1
• sin2ß B?fKs -0.5

Harnik,Larson,Murayama Phys.Rev.D69(094024),2004
hep-ph/0212180
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SM vs MSSM Bs?µµ-
MSSM parameter scan
A.Dedes, Mod.Phys.Lett.A18(2627),2003,
hep-ph/0309233
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B0?Xsµµ

• BR(B0?Xsµµ) well measured
• Additional handle FB-asymmetry
• Annual yield 4400 events, S/B3

Ali et al Phys.Rev.D61(074024),2000, hep-ph/991022
1
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Comparison to other experiments
Bs?Dsp Tevatron LHCb ATLAS
Mass resolution (MeV) 20 14 46
t resolution (fs) 100 40 100
Tagging eD2 () 1.4 6 4
L (fb-1) 0.4 2 30
years 1 1 3
Bs?Dsp 900 80k 8k
S/B 2 3 gt1
GENERAL Tevatron LHCb ATLAS/CMS
vs (TeV) 2 14 14
s(pp? bb)(µb) 100 500 500
L (cm-2s-1) 2008 4.1031 2.1032 1033

• Numbers obtained from various presentations in
  the last year
• No explicit blessing, just implicit...

Bs?µµ Tevatron LHCb ATLAS CMS
PTµ min (trigger) 2 1.2 6 3
L (fb-1) 2 10 10
Mass resolution (MeV) 90 18 80 46
Bs?µµ / year 1 30 9 7
background / year 4 lt100 lt20 lt1
Bs?J/?f Tevatron LHCb ATLAS CMS
L (fb-1) 0.260 2 30 10
years - 1 3 1
Bs?J/?f 203 120k 300k 50k
S/B 2 3 3 10
s(sinfs) - 0.06 0.04 0.028
BR _at_90CL lt7.10-9
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SU(5) The simplest GUT

• The simplest GUT is SU(5)
• 24 gauge bosons
• 8 gluons
• 4 W,Z,?
• 12 bosons
• 3 coloured Y (q-1/3)
• 3 coloured X (q-4/3)
• X,Y sometimes called leptoquarks or Higgs
  triplets
• B, L violated, but B-L conserved

24 Bosons

• Structure
• Fermions 10 ?5
• ?5 ( 1,2) (?3,1)
• 10 ( 1,1) (?3,1) ( 3,2)

• Note
• From?5 follows qd1/3 qe
• From 10 follows qu-2 qd
• Relation between charge and color

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GUT Proton decay
mp935 MeV

• Super-Kamiokande limits
• tpgt5. 1033 years
• Corresponding to lt1 kg of the earth

Phys.Rev.Lett.81 (3319) 1998, hep-ex/9806014
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SO(10)
1

• SO(10) ? SU(5) x U(1)
• 16 10 ?5 1
• Fermions 10Q,uc,ec ?5 dc,L 1 ?R
• Multiplets like (srR,sbR,sgR,?µL,µL) and
  (brR,bbR,bgR,?tL,tL)

10

• So, SO(10)
• unifies all fermions in 1 multiplet
• breaks simply to the Standard Model
• explains bizarre charge assignments
• obtains unification (in its supersymmetric
  version)
• accomodates p decay bounds (due to big MGUT)
• includes the right-handed neutrino

SU(5)

• Question
• What does the presence of the right-handed
  neutrino imply, given the neutrino mixing?

?5
31
The model SUSY SO(10)

• Why SO(10) ??
• Small extension of SU(5)
• SO(10) ? SU(5) x U(1)
• 16 10 ?5 1
• It nicely incorporates the right-handed ?
• The see-saw mechanism explains small non-zero
  neutrino mass, and even relates M?R?MGUT
• It relates neutrino mixing to squark mixing

Superpotential (16 are fermions, 10 Higgses)

• YU contains the large top coupling
• YU can be symmetric. In Yu diagonal basis we have

• Break to SU(5)

• Break to MSSM (rh ?)

Hu, Hd vu/vdtanß
Neutrino mixing angle
bR
Without neutrino mass, UMNS could be rotated away
Chang, Masiero, Murayama Phys.Rev.D67 (075013),
2003, hep-ph/0205111
32
S0(10) and see-saw

• So SO(10)
• contains the right handed neutrino
• Its mass arrises naturally through the see-saw
  mechanism
• M?R v2/m?
• M?R (246 GeV)2/0.05eV 1015GeV
• GUT scale 1015 GeV
• ? coincedence?

33
Neutrino masses seesaw

• Dirac masses

? ??

• Majorana mass for right-handed ?

From neutrino mixing
Relation between m?, MEW, MGUT
34
Neutrino mixing SNO
8B ??e
MSW oscillations ?e??µt
?m28.0 10-5 eV2, tan2?120.45
?m25.0 10-5 eV2, tan2?120.34
SNO Coll., Q.R. Ahmad et al. Phys.Rev.Lett.89
(011302),2002, nucl-ex/0204009
SNO Coll., Q.R. Ahmad et al. Phys.Rev.Lett.89
(011302),2002, nucl-ex/0204009, nucl-ex/0502021
35
EDM of the Neutron

• Standard Model dnlt10-31 e cm
• A nonzero value is forbidden by P- and
  T-invariance
• SUSY dnlt10-25 e cm

Laboratory Limit year
ILL lt1.2 10-25 90
PNPI lt0.97 10-25 96
ILL lt0.63 10-25 99
ILL lt1 10-26 04
PSI lt2 10-28 05
LANL,ILL lt5 10-28 10?
Phys.Rev.Lett.82(907),1999
J.Ellis, Nucl.Instrum.Meth.A284(33),1989
36
µ?e ?
J.Hisano et al.,Phys. Lett. B391 (1997) 341 R.
Barbieri et al.,Nucl. Phys. B445(1995) 215

• Experimental Limit (MEG Coll. At PSI)
• BR(µ?e ?)lt1.2 10-11
• BR(µ?e ?)SM0

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Not only SUSY can cause observable effects
Composing new models which seek to explain the
observed hierarchy of masses and the CKM matrix
is a cottage industry, with very fruitful
discussions between theory and experiment
38
B mixing
Decay probability
39
CKM
40
Computing Dmd Mixing Diagrams
GIM(i.e. VCKM unitarity) if u,c,t same
mass, everything cancels!
Dominated by top quark mass
41
LHCb yields and background
Nominal year 1012 bb pairs produced (107 s at
L2?1032 cm?2s?1 with ?bb500 ?b) Yields include
factor 2 from CP-conjugated decays Branching
ratios from PDG or SM predictions
R.Forty, CKM 2005
42
Baryon Asssymetry
Buchmüller, Wyler Phys.Lett.B521 (291),2001
hep-ph/0108216

1. Leptogenesis
2. Baryogenesis through sphaleron