Flavour Physics at Lhcb

Flavour Physics at LHCb

Michael Schmelling – MPI for Nuclear Physics e-Mail: [email protected]

Overview Introduction CP-Violation Measurements B-Physics with LHCb Selected Decay Channels Summary

Flavour Physics at LHCb Michael Schmelling / June 8, 2006 page 1 1. INTRODUCTION

Why B-Physics ? – or – Where is all the Anti-Matter? naive expectation: equal amounts of matter and anti-matter from the Big Bang, but... for example, no annihilation radiation seen in γ-rays from space, or search primordial He so far without positive results...

10-1 look for: Smoot et al. (1975) 10-2 Aizu et al. (1961) Evenson (1972) § cosmic ray He 10-3 Evenson (1972) Smoot et al. (1975)

§ go into space Badhwar et al. (1978) § atio 10-4 Golden et al. (1997) AMS experiment Buffington et al. (1981) 10-5 Result: BESS (93, 94, and 95 flights) 10-6 AMS STS-91(1998) no He found Preliminary

10-7 Antihelium / helium flux r

10-8

AMS on ISS 10-9 NASA

AMS OV-103

-10 10 -1 -2 10 1 10 10 Discovery 1 2 3 4 5 6 7 8 9 10 11 12 13 Rigidity (GV) Payloads SM-Spacehab

Flavour Physics at LHCb – Introduction Michael Schmelling / June 8, 2006 page 2 Zakharov’s Conditions

The necessary conditions to explain the matter dominance of the universe are: 1. C- and CP-violation 2. baryon-number violation 3. thermal non-equilibrium Standard Model: C- and CP-violation exist in CKM-sector baryon-number violation via Spalerons and thermal non-equlibrium can be created in a 1st order phase transition during the early universe

Problem: SM-Higgs particle is too heavy to generate the 1st order phase transition and the CP-violation in the CKM-sector is too small to explain the matter dominance of the universe § extra sources of CP violation are needed § “New Physics” expected in CP-violation measurements

Flavour Physics at LHCb – Introduction Michael Schmelling / June 8, 2006 page 3 2. CP-VIOLATION MEASUREMENTS

CP-Asymmetry ACP for decays into a ﬁnal state y:

Γ(X → y) − Γ(X → y¯) 2 ACP = with partial widths Γ(·) = |a(·)| Γ(X → y) + Γ(X → y¯)

Consider mixing induced CP-violation in decays to a CP-eigenstate y = yCP :

a(X→yCP ) = am(X→X) · ad(X→yCP ) + am(X→X) · ad(X→yCP )

The contributing amplitudes are:

a (X→y ) a (X→X) ∆mt a (X→X) ∆mt d CP = Aeiω m = cos m = i sin eiφ ad(X→yCP ) am(X→X) 2 am(X→X) 2

with phase factors

phase from the decay: ω ACP = − sin(∆mt) sin(φ − 2ω) mixing phase: φ §

Flavour Physics at LHCb – CP-Violation Measurements Michael Schmelling / June 8, 2006 page 4 CKM Matrix and Unitarity Triangles

Standard Model: All phases arise from CKM Matrix elements

Vud Vus Vub  Vcd Vcs Vcb  ≈ V V V  td ts tb  1 − λ2/2 λ Aλ3(ρ − iη)  −λ 1 − λ2/2 Aλ2  Aλ3(1 − ρ − iη) −Aλ2 1   Wolfenstein-parametrization

? ? unitary matrix, i.e. Ci · Cj = Ri · Rj = δij, parametrized by 4 free parameters qualitative picture determined by λ ≈ 0.22 ? ? unitarity triangles C1 · C3 = R3 · R1 = 0 § arg(Vtd) = −β (Bd-mixing) + − § arg(Vub) = −γ (Bd → π π decays) 2 § arg(Vts) = χ + π ≈ ηλ + π (Bs-mixing)

note: V 6= 1 goes beyond Higgs search in addressing the origin of mass!

Flavour Physics at LHCb – CP-Violation Measurements Michael Schmelling / June 8, 2006 page 5 Phenomenology of B-decay Channels

from R. Fleischer hep-ph/0505018v1

Flavour Physics at LHCb – CP-Violation Measurements Michael Schmelling / June 8, 2006 page 6 Search for New Physics in B-Decays

compare measurements which are insensitive to new physics with measurements of the same quantity from a decay channel that is sensitive to new physics § β from Bd → J/ψ Ks - tree level dominates § β from Bd → φKs - pure penguin § γ from Bs → DsK - tree level dominates § γ from Bd → πK - with penguin contribution study observables which have a small expectation value in the standard model § CP-asymmetry in Bs → J/ψ φ § transitions sensitive to FCNC, for example B → K?γ i.e. b → sγ 0∗ + − Bd → K µ µ + − rare decays Bd,s → µ µ compare UT from length and angle measurements Note: The discussion here focuses on mixing induced CP-violation. In addition also direct CP- violation can be measured, with usually different sensititivity to New physics...

ACP (t) ∼ Adir cos(∆mt) + Amix sin(∆mt)

Flavour Physics at LHCb – CP-Violation Measurements Michael Schmelling / June 8, 2006 page 7 3. B-PHYSICS WITH LHCb

Kinematics of b-quark production: Challenges to the detector:

EFFICIENT TRIGGER FOR NON-LEPTONS DISTINGUISH π/K

∗ ∗ ∗ B→D π,D 3π B → DK B → ρπ B → K∗γ RESOLVE xs

Bs → K K B → D π Bs → J/ψφ 3 s s θ B → D K b s s [r 2 + − ad 3 B → D D ] 2 ] d,s d,s d,s ∗+ ∗− → 1 [rad Bs → K K Bs J/ψKs 1 θb 0

B → ρ+ρ− B → ππ B → K∗0K∗0 B → Kπ

10 2

Bd → J/ψKs

0 10 Bd → J/ψρ

+ − −9 Bs,d →µ µ (O(10 )!)

1 -2 0 2 4 6 § LHCb: optimized to meet these requirements

Flavour Physics at LHCb – B-Physics with LHCb Michael Schmelling / June 8, 2006 page 8 The LHCb Experiment

§ forward spectrometer § excellent particle-ID § high vertex resolution § ﬂexible trigger 1 MHz readout to HLT 2 kHz to disk

pp interactions/BX

L = 2 · 1032 cm−2s−1, adjustable 105 b-events/second, 2 · 1012 b-hadrons/year 0 B : B : Bs : Λb ≈ 0.8 : 0.8 : 0.2 : 0.2 lepton and hadron trigger 200 Hz exclusive B-candidates 600 Hz high mass Di-muons 300 Hz D∗ candidates 900 Hz inclusive b-trigger

Flavour Physics at LHCb – B-Physics with LHCb Michael Schmelling / June 8, 2006 page 9 LHCb Monte Carlo Simulation

detailed description of detector material and magnetic field full pattern recognition, trigger simulation (incl. HLT) and offline event selection realistic inefficiencies, noise hits and pile-up from previous bunch crossings

Flavour Physics at LHCb – B-Physics with LHCb Michael Schmelling / June 8, 2006 page 10 Flavour Tagging

§ determination of the initial ﬂavour of a B-meson

obvious for charged B-mesons signal B + + π µ experimental challenge for neutral B-mesons K S 1.1m π − Hera proton 0 34GeV § opposite side tagging 920 GeV B µ − 9 mm reconstruct ﬂavour of “idler”-B 120 GeV 96 nsec BX - B - e § same-side tagging 4 I.A./BX 8 wire - ?? targets K self-tagging B -decays D 0 17GeV tagging B > 0.5 fragmentation products εT LHCb Flavour tagging performance: note: effective fraction of perfect tags

2 εeff = εtag(1 − 2w) with

§ εtag tagging efﬁciency § w mistag fraction

Flavour Physics at LHCb – B-Physics with LHCb Michael Schmelling / June 8, 2006 page 11 4. SELECTED DECAY CHANNELS

The “golden Decay” Bd → J/ΨKs d d 0 Ks s Bd Vcs c J/Ψ ? c b Vcb

§ “classical” example for mixing induced CP-violation § in Wolfenstein-parametrization no phase from decay § in Standard-Model measures the Bd-mixing phase § dominated by tree level contributions § small or no New Physics contributions expected § Measurement of sin 2β

Flavour Physics at LHCb – Selected Decay Channels Michael Schmelling / June 8, 2006 page 12 0 The Decay B → φKs

Standard Model: alternative way of measuring sin 2β in a pure penguin mode W

? Vtb t Vts b s φ g s Bd s 0 Ks d d 2 the weak phase from decay is dominated by arg(Vtd) which is O(λ )

W − H− § possible contributions from new physics: new heavy bosons with CKM-like couplings b u, c, t s b u, c, t s new contributions to FCNC transitions − ˜ would show up elsewhere as well χ g constrained by other limits s s b u˜, c,˜ t˜ b d,˜ s˜, ˜b

Flavour Physics at LHCb – Selected Decay Channels Michael Schmelling / June 8, 2006 page 13 Results from the B-Factories

eff eff HHFF AAGG sin(2β )/sin(2φ1 ) Moriond 2006 PRELIMINARY b→ccs World Average 0.69 ± 0.03 +0.07

HFAG 0.50 ± 0.25

0 BaBar -0.04 Moriond 2006 K Belle 0.44 ± 0.27 ± 0.05 φ n = 16 measurements Average HFAG 0.47 ± 0.19 Moriond 2006 0 BaBar 0.36 ± 0.13 ± 0.03 14 below b → cc¯s K Belle 0.62 ± 0.12 ± 0.04 η′

Average HFAG 0.50 ± 0.09 +0.23 consider the probability that from

Moriond 2006 0.95 ± 0.10 S BaBar -0.32

K Belle 0.47 ± 0.36 ± 0.08 n measurements which ﬂuctuate 0 f

Average HFAG 0.75 ± 0.24 +0.30 Moriond 2006 S BaBar 0.35 -0.33 ± 0.04 symmetrically around the b → cc¯s

K Belle 0.22 ± 0.47 ± 0.08 0 π

S average, at most M = 2 are above: Average HFAG 0.31 ± 0.26 K BaBar Moriond 2006 -0.84 ± 0.71 ± 0.08 0 π

Average -0.84 ± 0.71

0 M HFAG +0.35 π 0.51 ± 0.02 S BaBar -0.39

Moriond 2006 +0.12 −n n K Belle 0.95 ± 0.53 -0.15 p = 2 ≈ 0.0021 ω Average HFAG 0.64 ± 0.30 k S k=0 BaBar Moriond 2006 0.17 ± 0.52 ± 0.26 X K 0 Average 0.17 ± 0.58 ρ 0 BaBar HFAG 0.41 ± 0.18 ± 0.07 ± 0.11 § 3 . . . K -sigma effect stay tuned! - Moriond 2006 +0.19 Belle 0.60 ± 0.18 ± 0.04 -0.12 K +0.11 +

Average HFAG 0.51 ± 0.14 -0.08 S K +0.28

Moriond 2006 0.63 ± 0.04 K BaBar -0.32 S Belle 0.58 ± 0.36 ± 0.08 K S Average HFAG 0.61 ± 0.23 K Moriond 2006 -3 -2 -1 0 1 2 3

Flavour Physics at LHCb – Selected Decay Channels Michael Schmelling / June 8, 2006 page 14 The Decay Bs → J/ψ φ

V t V ? q tq tb b q q s¯

0 0 Bq Bq Vcs c ¯ ? q¯ ¯ ? c¯ b Vtb t¯ Vtq b Vcb

similar to the “golden decay” Bd → J/ψ Ks with d → s theoretically clean measurement, only very small penguin contribution 2 2 only small CP-asymmetry expected in SM: φs = − arg Vts ≈ −2ηλ ≈ −0.04 sensitive probe to NP, e.g. § gluinos and squarks in box diagram: sin φs ∼ 1 (Ball et al., hep-ph/0311361) § up-type quark singlets: sin φs ∼ λ (Aguilar-Saavedra et al., hep-ph/0406151) mix of different CP eigenstates because two CP-odd vector mesons in ﬁnal state § CP-even states from scalar 0 and longitudinal || polarization § CP-odd states from transverse ⊥ polarization study also ﬁnal states which are CP-eigenstates, e.g. § Bs → J/ψ η, Bs → ηcφ, . . .

Flavour Physics at LHCb – Selected Decay Channels Michael Schmelling / June 8, 2006 page 15 −1 LHCb Sensitivity for φs with 2 fb

§ dealing with different CP-Eigenstates

standard measurement for CP-Eigenstates angular analysis for Bs → J/Ψφ

dΓ 2 2 3 2 2 3 2 ∝ |A0| + |A | (1+cos Θ )+|A | sin Θ d cos Θ || 8 tr ⊥ 4 tr tr § Results (L. Fernandez/J. van Hunen)

Channel CP-Eigenstate σ(φs)[rad] Bs → J/Ψφ mixed 0.023 Bs → DsDs even 0.133 + − 0 Bs → J/Ψη(π π π ) even 0.129 Bs → J/Ψη(γγ) even 0.108 Bs → ηvφ even 0.108 combined 0.021

Flavour Physics at LHCb – Selected Decay Channels Michael Schmelling / June 8, 2006 page 16 + − The Decay Bd → Xµ µ

− − l l l+

γ/Z l+ W ν W b s b s t t

q q q q

many possible New Physics contributions ∗ SM § in bsγ-vertex, which contributes also to B → K γ with ACP ≤ 0.01 § extra Z-bosons § new particles in box diagrams theoretically rather clean prediction for inclusive processes and ratios still good accuracy for experimentally accessible exclusive ﬁnal states + − ∗ § Bd → Xµ µ with X = K , ρ, φ § study FB-asymmetry of the muons w.r.t. their common momentum . . .

Flavour Physics at LHCb – Selected Decay Channels Michael Schmelling / June 8, 2006 page 17 ∗ + − SM vs SUSY Predictions for Bd → K µ µ

forward-backward asymmetry LHCb sensitivity after 5 nominal years 2 § SM predicts zero around s = 3 Gev § 22k events 2 § very small hadronic uncertainties § zero point s0 = 4.0 0.5 GeV eff § supersymmetry naturally expects § constraint on C7 no change of sign note: only continuum is shown – contributions from J/Ψ, Ψ0 etc. are suppressed

Flavour Physics at LHCb – Selected Decay Channels Michael Schmelling / June 8, 2006 page 18 5. SUMMARY

B-Physics at LHC is a excellent place to look for new physics § many ways to look for New Physics by overconstraining the SM SM (tree level) dominated measurements penguin dominated processes box diagram dominated decays § comparison of results will reveal New Physics § sensitivity to new particles in quantum corrections up O(TeV) LHCb is optimized to exploit the B-Physics potential of LHC § dedicated to study of B-physics and rare decays § full physics potential from day-1 of LHC § precision measurements of couplings § “worst case” will be precision measurements of CKM matrix historical precedent: Tycho Brahe . . . potential for charm physics not yet explored thinking has already started towards upgrades . . .

Flavour Physics at LHCb – Summary Michael Schmelling / June 8, 2006 page 19 LHCb Sensitivities for 2 fb−1

Flavour Physics at LHCb – Summary Michael Schmelling / June 8, 2006 page 20