To Infinity and Beyond ! S-LHCb OR “How I stopped worrying and learnt to love what we can do with 0.1 quadrillion* B’s.” OR “Who will be the true superhero of 2015 flavour physics ?” * 1014 – B’s produced at Super-LHCb over 5 years 1 Physics Opportunities at an Upgraded LHCb Edinburgh Upgrade Workshop, 11/1/06 Guy Wilkinson, University of Oxford with thanks for useful input to: Robert Fleischer, Franz Muheim, Tobias Hurth, Ulrik Egede, Vanya Belyaev 2 Contents Why plan for B-physics beyond ~2015? Scenarios for discussion. Definitions and assumptions Selected topics: • Super-precise angle measurements: Φd, Φs and γ • Non-SM CPV phases in b→s Penguins • b→sll, b→dll and b→(s,d)γ • Bd,s→μμ • Beyond the B: τ and charm physics (Will try my best to motivate interest of each and quantify performance – but there will be a fair amount of guesswork.) Conclusions 3 Comparisons with Super-B Won’t be showing plots like this → (Unlike Browder @ CKM 2006) SuperKEKB at 50 ab ΔS(φKs) + ΔS(K K Ks) ΔS(η’Ks) ΔS(KsKsKs) 0 ΔS(π Ks) sin2χ(Bs → J/ψφ) *0 S(K γ) Br(B → Xsγ) ACP(B → Xsγ) *+C9 w/ AFB(K l l ) *+C10 w/ AFB(K l l ) + Br(Bs → μ μ ) + + Br(B → K νν) + Br(B → Dτν) 0 Br(B → Dτν) sin2φ1 φ2(ππ isospin) φ2(ρπ) (*) φ3(DK ) φ3(Bs → KK) φ3(Bs → DsK) |Vub| -1 -1 LHCb (0.002 ab ) ΔS(φKs) + ΔS(K K Ks) ΔS(η’Ks) ΔS(KsKsKs) 0 ΔS(π Ks) sin2χ(Bs → J/ψφ) *0 S(K γ) Br(B → Xsγ) ACP(B → Xsγ) *+C9 w/ AFB(K l l ) *+C10 w/ AFB(K l l ) + Br(Bs → μ μ ) + + Br(B → K νν) + Br(B → Dτν) 0 Br(B → Dτν) sin2φ1 φ2(ππ isospin) φ2(ρπ) (*) φ3(DK ) φ3(Bs → KK) φ3(Bs → DsK) |Vub| -0.5 -0.3 -0.1 0.1 0.3 0.5-0.5 -0.3 -0.1 0.1 no info no info no info 0.3 0.5 4 Comparisons with Super-B Won’t be showing plots like this → (Unlike Browder @ CKM 2006) Several entries badly wrong, and apart from this, misleading: • obscures relative importance of measurements, & requirements on precision LHCb (0.002 ab ) ΔS(φKs) + ΔS(K K Ks) ΔS(η’Ks) ΔS(KsKsKs) 0 ΔS(π Ks) sin2χ(Bs → J/ψφ) *0 S(K γ) Br(B → Xsγ) ACP(B → Xsγ) *+C9 w/ AFB(K l l ) *+C10 w/ AFB(K l l ) + Br(Bs → μ μ ) + + Br(B → K νν) + Br(B → Dτν) 0 Br(B → Dτν) sin2φ1 φ2(ππ isospin) φ2(ρπ) (*) φ3(DK ) φ3(Bs → KK) φ3(Bs → DsK) |Vub| -0.5 -0.3 -0.1 0.1 0.3 no info no info no info l! fu elp • selective (eg. no Bs→ΦΦ) ΔS(φKs) + ΔS(K K Ks) ΔS(η’Ks) ΔS(KsKsKs) 0 ΔS(π Ks) sin2χ(Bs → J/ψφ) *0 S(K γ) Br(B → Xsγ) ACP(B → Xsγ) *+C9 w/ AFB(K l l ) *+C10 w/ AFB(K l l ) + Br(Bs → μ μ ) + + Br(B → K νν) + Br(B → Dτν) 0 Br(B → Dτν) sin2φ1 φ2(ππ isospin) φ2(ρπ) (*) φ3(DK ) φ3(Bs → KK) φ3(Bs → DsK) |Vub| -1 -1 tH No • don’t compare like-with-like (5 years Super-B from 2015 with 1 year of LHCb in 2008) SuperKEKB at 50 ab 0.5-0.5 -0.3 -0.1 0.1 0.3 0.5 I will however make case-by-case topic comparisons with Super-B. But remember my selection is LHCb inspired. (But it is not narrow!) 5 Why B-physics beyond 2015, & why at LHCb ? Testing the flavour structure of the SM has taken many years. Elucidating the flavour structure of the NP found at the LHC will surely not be a simple task. Either: LHCb will find exciting NP signal (eg. Bs→μμ or Φs enhancement, UT non-closure at ~5o level). In this case there will be a host of follow up measurements, all of which will benefit from more statistics/better experiment. → script will write itself – so don’t consider further Or: ATLAS & CMS will find NP, but no big signatures in flavour sector. For instance Minimal Flavour Violation (MFV) might give identical CPV to SM, but give (possibly small) deviations in b→(d,s) Penguins and Bd,s→μμ → important to test SM predictions in CPV down to the level of the theoretical predictions (and the theory in 2020 [and beyond?], not now! ) → make improved studies of b→(d,s) Penguins and rare decays in measurements which will be statistically limited at LHCb. Both motivate flavour physics beyond 2015. But why at LHCb? This talk ! 6 Definitions and Assumptions Unless stated otherwise names and numbers will refer to the following: ‘LHCb’ 10 fb-1, ‘Super-LHCb’ 100 fb-1, ‘Super-B’ 50 ab-1 For Super-LHCb I merely extrapolate present statistics assuming identical trigger and reconstruction performance (unlikely to be true). For Super-B numbers I either take values from recent talks (eg. flavour workshop) or reports, or I extrapolate from existing B-factory results. For Super-LHCb I do not (cannot) estimate the contribution of experimental systematics. Bear this in mind, but also recall that we intend to determine our main systematics (eg. tagging, τ resolution…) from data. Also at LHCb: σ calibration signal >>> σ physics signal and so it is reasonable to hope that experimental systematics can be controlled. Theory errors I discuss where relevant, although some of my extrapolations are arbitrary and mostly for illustration purposes. But improvements in theory estimates (esp. lattice QCD) are crucial aspects of any upgrade argument. 7 Progress with theory Increase in computing power is very likely to lead to significant improvements in any quantity which can be calculated on the lattice Pre-LHCb 2010 2014 6 TFlop year 40 TFlop year 1 PFlop year 11% 5% 4% 2% 13% 5% 4% 2% ξ 5% 3% 2.5% 1.5% Vub-excl.* 11% 6% 5% 3% Vcb-excl.* 4% 2% 1.5% 1% Now B̂ K f Bs B̂ Bs (table courtesty of Vagnoni talk, CKM 2006 Nagoya) In addition, there will be a wealth of precise BR measurements against which theorists can tune and test these and other calculations. → Expect significant improvements in many areas before 2015-20 8 Why measure β to < 1% ? Surely post LHCb, β will be known as well as we need to. Why go further ? “Because it’s there!” George Mallory (lost on Everest 1924) sin2β LHCb-upgrade project leader It is the parameter of the UT we can measure most precisely, so we should. Also we should note that the (final) indirect constraint will be very stringent ! 9 Measuring β at the sub-percent level (< 0.2o) Direct measurement of Φd (=2β in the SM) is tested against indirect prediction which is fixed by Rb (the Vub/Vcb side) Rb now known to 7% from Vub inclusive → translates into β indirect of 1.6o Compare with (Super-)LHCb stat error: (Super-)LHCb 2 fb-1 σ (stat) 0.66o 10 fb-1 100 fb-1 0.30o 0.09o Rb β Looks OK… but precision on Rb will improve as lattice improves Vub exclusive. Must plan for Rb precision of ~2% → β indirect error then 0.5o Also here experimental systematics will be a major consideration. Maybe we will have to be stricter in choice of events (eg. tagging) to keep σsyst ≤ σstat ? All good arguments for > 10 fb-1 ! 10 Controlling Penguins in sin2β If we plan a very precise measurement of β we must worry about the Penguin pollution. (This probably mandatory at LHCb, not just Super-LHCb). One method which has been proposed (Fleischer, Eur.Phys.J. C10 (1999) 299) is to measure the CP asymmetries in Bs→J/ψKS and relate these to Bd→J/ψKS through U-Spin (good approximation for 1st order correction ?) BR for Bs mode ~ 2 x 10-5, so we will have 80 x fewer events than for Bd→J/ψKS Previous LHCb attempt to show feasibility (1999 workshop) had B/S>>1. But we should be able to do better… Worth evaluating precision of approach at LHCb and Super-LHCb 11 A precision measurement of Φs Initial hope in measuring Φs (= -2ηλ2 in SM) with, say, J/ψΦ, is that NP will manifest itself through significantly larger value than v. small SM expectation. But situation could be as in Bd system where any NP phase < few degrees Prepare for precise measurement, noting that in SM Φs is very well constrained: Φs indirect = -0.037±.002 Compare with (Super-)LHCb statistical reach: (Super-)LHCb 2 fb-1 10 fb-1 100 fb-1 0.021 0.009 0.003 σ (stat) 10% measurement (modulo systematics) Note however that here also we must worry about Penguins, and their relative effect could be large compared with this precision. Control with Bd→J/ψρ (Fleischer, Phys.Rev. D60 (1999) 073008) . 12 Goal for the ultimate γ measurement Geometry of UT is such that the mixing side (Rt) dominates in indirect prediction of angle γ . Thus tree-level γ measurement in conjunction with knowledge of Rt can be used to probe for new physics contributions to the latter. γ Rt Present situation already tells us that a precise test is needed ! Uncertainty on γ from sides (UTFIT) = 6o Lattice improvements will lead to shrinking of this error – let us guess by a factor of 5 to 10 at t=∞. So is it possible to measure γ to 0.5-1 degree ? 13 γ expectations at LHCb Many ways to measure γ through tree-level processes at LHCb. Include: 1. Bs→DsK, precision of ~14o / 2 fb-1 2. Bd→D(*) π, requires external input on rB or U-Spin 3. B±,Bd→D(*)K(*) , with the D0 decaying to: 2 bodies: πK, KK, ππ 3 bodies: Ksππ, KsKK, KsKπ 4 bodies: Kπππ, KKππ best modes offer 5-10o precision each for 2 fb-1 A not outrageous expectation is that with 10 fb-1 we could achieve a precision of ≤ 3o. Based on approaches 1. and the best understood modes of 3., together with guesses about likely evolution of Dalitz modelling errors. This would make a major impact on today’s UT, but does not meet our ultimate goal of 0.5-1o . What then can we hope for at Super-LHCb ? 14 Prospects for a sub-degree error on γ In extrapolating to 100 fb-1 it is only reasonable to consider strategies which are theoretically clean &/or where performance and each is well-understood. In the LHCb era we will be able to benefit from the combined information of many DK modes. Some will have associated (eg.) modelling errors which will (probably) prove limiting in ultra-precise regime. The √N law will not apply ! So today focus on 3 modes: LHCb (10 fb-1) Super-LHCb (100 fb-1) Super-B (50 ab-1) DsK 27 k 270 k / D(Ksππ)K ≤ 25k ≤ 250k 46k D(Kπ)fav K 280k 2.8 M 89k GW extraps from published B-factory analyses One immediate observation: Super-B will struggle to match LHCb results… 15 Prospects for a sub-degree error on γ What γ sensitivity could we hope for with these modes at Super-LHCb ? 1. Bs→DsK: here use naïve √N → 2o for 100 fb-1 2. D(KSππ)K Dalitz Likely that statistical precision will be ~ 2o (better than Super-B !) Error associated with knowledge of Dalitz space is at present crippling (10o), but it is certain to reduce, in particular due to CP-tagged data gathered at CLEO-c and BES-III (→). Down to 2-4o ? (Similar trick will be possible with KSKK/KSKπ and 4-body modes) 3. D(two body)K D→hh modes are clean and statistics huge, but with these alone the problem is barely constrained. Either: a) add 4-body channel (Kπππ) , b) add CP-odd eigenstate (eg. ΦKs), c) or exploit D*→D0(π,γ) trick. Not possible to give headline number today, but no one mode will dominate 16 CP tagged D0 decays at the ψ(3770) Asner, CKM 2006 17 CP tagged D0 decays at the ψ(3770) (ctd) Asner, CKM 2006 18 New Physics phase in b→s Penguins ? sin2βeff measurements that involve b→s Penguins show intriguing bias w.r.t. charmonium results. Naïve average gives 2.6 sigma discrepancy. Consistent sign of bias throughout channels is tantalising (theory correction generally has other sense…) Still, it is perhaps more correct to average only 3 cleanest channels, → ΦKS, η’KS and KSKSKS 19 Size of NP hint and Timescale for Discovery GW average of present ΦKS, η’KS and KSKSKS results (~1 ab-1) ‘Discrepancy’ = 0.13 ± 0.08 Ergo, with present central value there will be no 5σ discovery at Belle/BaBar. Super-B projections for 50 ab-1 : ΦKS error ≈ 0.030 η’KS error ≈ 0.025 (includes systematics) Only ΦKS really possible at LHCb. Here statistical precision of 0.32, 0.14 and 0.05 expected with 2, 10, 100 fb-1 (extrap. from Yuehong). (Although could Super-LHCb be optimised with this decay in mind ?) Apparent conclusion: Super-B a better bet for discovery. 20 BS→ΦΦ at (Super-)LHCb Best way to probe b→s Penguin phase at LHCb is through Bs→ΦΦ. W− Accesses same physics as B-factory Bd modes and should be theoretically very clean (how clean ?) ⎧b ⎪ 0⎪ Bs ⎨ ⎪ ⎪⎩ s t g s⎫ ⎬φ s⎭ s⎫ ⎬φ s⎭ Reconstruction studies (Bruno de Paula) predict 4000 events / 2 fb-1 (with 60% uncertainty due to B.R.) and 0.4 < B/S < 2.1 (90% C.L.) Sensitivity studies (Xie) based on full angular analysis gives σ (ΦNP) ≈ 0.10 for 2 fb-1 , where ΦNP can be considered as NP phase driving sin2β ‘anomaly’ Precision post LHCb 0.044 – good, but no cigar! (‘only’ 2.9σ) Precision post Super-LHCb 0.014 – as good as we need? (~ ΦKS theory limit) Extremely promising – looks a very good reason for an upgrade, and is (more than) competitive with Super-B. But more work needed to quantify potential. 21 B→K*μμ at Super-LHCb and Super-B Interest and potential of K*μμ well established. Headline measurement is the New-Physics-sensitive 0 point in the forward-backward asymmetry. Recently, attention focused on problems introduced by non-resonant background. Solution may dilute statistical sensitivity… but this will not be a concern at Super-LHCb 2 fb-1, gives 7.7k events. Fit AFB → LHCb, 2 fb-1 ( s0 true = 4.10 ) s0 = 4.11 ± 0.52 GeV2 (13% error) And 10 fb-1 gives 39k events (7% error on s0) So in 100 fb-1, 385k events (2.1% error on s0) Mμμ2 (GeV2) Extrapolate current Belle numbers to 50 ab-1 → 16k events 22 How clean is s0 in K*μμ? Super-LHCb would make very precise measurement of s0 (and Super-B ≈ 2 years of LHCb). But what is the theoretical uncertainty ? NLO contribution calculated within QCD factorisation (Beneke, Feldmann, Seidel) ~ 9% uncertainty Similar size, but hard to estimate, error from 1/mb power corrections So present error is in 10-15% ballpark. So s0 alone is not a very strong argument for Super-LHCb… Two caveats: - treatment of non-resonant background may degrade precision / fb-1 - it is surely reasonable to hope for some improvement in error by 2020 ?! 23 Inclusive vs exclusive AFB in B→sμμ Nice advantage of (Super-)B environment is opportunity of making inclusive measurements. Such an approach attractive since theory error < exclusive case. In AFB zero-point analysis: Inclusive theory error ~ 5 % Exclusive theory error ~ 10-15% (Numbers courtesy Tobias Hurth) Situation at present – could improve before 2015-2020 Whereas experimental (statistical) precision on s0 is: Super-LHCb - 100 fb-1 (exclusive) 2 % Super-B – 50 ab-1 (semi-inclusive) 7 % (extrap. from SLAC-R-709) (semi-inclusive in sense that 60% of decays are reconstructed) So inclusive analysis has marginal advantage, with present theory errors… 24 Other opportunities in K*μμ Other important observables in K*μμ system will almost certainly benefit from Super-LHCb statistics, eg. those considered in transversity angle analysis in which decay is described in terms of 4-variables: s θl θK* φ μμ mass squared AFB angle equivalent K* angle angle between K* and μμ decay planes In this basis can construct several asymmetries which at leading order depend on short range information only, in particular: 25 AT (1) and AT (2) vs Mμμ Variables appear theoretically rather clean ! (Kreuger, Matias, hep-ph/0502060) (no 1/mb error included) Moreover, very sensitive to New Physics effects through eg. RH currents in C7eff AT(2) with such contributions (note scale) A powerful way to probe chiral structure of b→s transitions (c.f. b→s gamma) 26 Initial LHCb studies of AT(2) sensitivity Initial LHCb studies (Egede) has demonstrated that AT (2) is extractable, using a toy-MC study in which Mμμ divided into 4-bins This result with 2 fb-1 (for more information see Oct. `06 Flavour Workshop talk and RD WG) For Super-LHCb shrink error bars by 7 (Super-B, by 1.4). Then one will be sensitive to the very small SM evolution, while still being an order of magnitude away from theory uncertainty. A very sensitive probe of b→s in which theory error is promisingly small ! 27 Studies of B→Xd l+l- ? All measurements we are interested in performing with B→sμμ are presumably equally interesting with B→dμμ, eg. as important test of MFV. b→s mode b→d mode b→d yield / 2 (→100) fb-1 Bd→K*μμ Bd→ρ(ω)μμ 10-100 (→ 500-5000) Bs→Φμμ Bs→K*μμ 10-30 (→ 500-1500) (self-tagging mode!) (Yields are GW guesses. Range expresses further guess as to effect of additional cuts w.r.t. b→s analogue required to further suppress background) Only possible at Super-LHCb ? Worth a more detailed look ! 28 Prospects with radiative Penguins Super-LHCb will accumulate very large samples of the ‘standard’ b→sγ events (eg. 3.7 million K*γ , 0.5 million Φγ). But we can also hope for: B→ωγ 2000 events in 50 ab-1, B/S < 3.5 (extrap. from existing study) B→ρ0γ : existing K*γ selection would give 50k events, but tighter cuts will be needed – awaiting DC06 studies W b t d t γ (Super-B expects around 3200 events in ρ0γ channel, but will also collect ρ±γ) Many interesting tests can be carried out with these events, eg. Vtd/Vts . Note that again the theory error on this exclusive measurement is not so bad: 7% (Ball, Jones and Zwicky hep-ph/061208), and there are also competitive lattice based results (Bechirevic, Lubicz and Mescia, hep-ph/0611295) Higher granularity/resolution ECAL would help, plus open other possibilities… 29 Hunting for Bs→K*γ b→dγ Penguin in the Bs system is Bs→K*γ. Cannot separate from the Bd decay with present ECAL, but maybe possible with improved resolution ? LHCb ECAL Factor 2 better energy resolution Bd→K*γ Bs→K*γ (Must also consider problem of combinatorial background) 30 Bs→μμ and Bd→μμ at Super-LHCb However, SM signal at 5σ still lies within reach of LHCb, although not comfortably so… Going further still: BR (x10-9) Hope for significant NP enhancements in Bs→μμ (but not in Tevatron range!) 10 9 8 7 6 5σ 5 4 SM prediction • Within SM and CMFV, signal 3σ BR is predicted to 10%. (Buras, hep-ph/0604057). Testing this cannot be done with 10 fb-1. • Rate of (Bd/Bs)→μμ is even more Integrated Luminosity (fb-1) tightly constrained in SM & CMFV. “ Bs→μμ/Bd→μμ = 32.4 ± 1.9 , one of magic numbers of CMFV ” (Buras) Matching such precision beyond even Super-LHCb (50-100 events?), but Bd→μμ observation could be, provided lepton id. can suppress Bd→ππ. 3 2 1 0 1 2 3 4 5 6 7 8 9 10 31 Accumulating Rare Charm Decays Super-LHCb has opportunity to collect a huge sample of valuable D0 decays (x 20 what could be accumulated at Super-B) LHCb (10 fb-1) Super-LHCb (100 fb-1) Super-B (50 ab-1) D0→K+K- 5 x 106 2.5 x 108 1.2 x 107 D0→K+π- 2 x 105 1 x 107 5 x 105 + D0 from B decays only. With present trigger scheme we expect same number again from primary charm. Could be enhanced with track/vertex trigger at L0 ? - These are events ‘on tape’. Tight cuts needed to suppress background and to partially reconstruct B to find D0 birth vertex for time dep. studies z res. of parent B (Patrick Spradlin) (lose factor of 3 and still have tails) 32 Opportunities in charm physics Sample sizes will allow for improving limits on mixing and CPV by 2 orders of magnitude w.r.t existing limits, eg. CPV in KK down to 10-4 Mixing exclusion plot 2006 The cynic: “ LHCb already has potential to see mixing & CPV at the level when it might be a NP signal (eg. 10-2 for CPV). Below that it is SM and dull ” The visionary: • duty to push on until mixing and CPV observed ! • any observation would be a new beginning for charm physics. Inevitably interest would focus on elucidating nature of phenomenon, and extending measurement programme: CPV in the mixing, triple products correlations in ρ0ρ0, CPV in other modes… Super-LHCb would be the experiment to answer this call ! 33 Lepton Flavour Violation Searches in τ decays An attractive feature of Super-B is its sensitivity to lepton violating τ decays τ→μγ τ→μμμ 3 x 10-8 3 x 10-9 -5 10 PDG2005 Belle BaBar -6 10 -7 10 -8 10 -9 10 μ−γ e−γ μ−π0 e−π0 − μη e−η μ−η′ e−η′ e−e+e− e−μ+μ− e+μ−μ− − + − μee μ+e−e− μ−μ+μ− e−π+π− e+π−π− − + − μππ μ+π−π− − + − eπK e−π−K+ + − − eπK − + − eKK e+K−K− μ−π+K− − − + μπK + − − μπK − + − μKK μ+K−K− e−ρ0 − e KS * e−K −– e K* e−φ μ−ρ0 − μ KS − * μK −– μ K* μ−–φ pγ – pπ0 Λπ− − Λπ In SM with neutrino mixing, LFV τ decays occur at ≤ 10-14 But other models predict values in range 10-10 – 10-7 Any observation of LFV in μ decays elsewhere would give this work extreme topicality Current B-factory limits are generally at a few 10-7, Super-B potential for 10 ab-1 (sensitivity to UL at 90% CL): Super-B with 10 ab-1 34 τ→μμμ at (Super-)LHCb Obvious LFV channel for us to search for is τ→μμμ. First looked at in 2000 (Bartalini) and is being re-visited now in the RD WG (Shapkin, Belous) Main source of τ’s at LHCb will be Ds→τυ. Total number of τ produced within acceptance for 1 year at Super-LHCb ~ 1012 (extrap. from Bartalini) So guessing a likely trigger & reconstruction efficiency of 5% (similar to Bs→μμ ?) one would expect ~50 τ→μμμ events / yr with a B.R. of 1 x 10-9 However, present LHCb studies have large background retention: 105 events in normal year of 2 x 1032 operation. Not good ! My questions: • What is this background? Guess mainly combinatoric (but decays such as B+→ω(π+π-π0)μ+υ will eventually be an irreducible problem) • What other cuts could be deployed? (Isolation cut not used?) Important topic which deserves more attention (even at LHCb) – we should understand our potential. Nice test-case for Super-LHCb vertex detector ? 35 Conclusions Clear need for an upgraded heavy flavour programme beyond 2015. Lattice improvements will motivate better γ and (to an extent) Φd (β) measurements. S-LHCb is the best place to do this. NP in the Bs sector may be small → precise Φs measurement valuable. Bs→ΦΦ looks to be a very sensitive probe of NP phases in b→s, and competitive with Super-B possibilities. There are NP sensitive studies in exclusive b→sμμ which will be statistics limited at LHCb. Doubly so for b→dμμ and d γ . (Super-B inclusive? Evolution of exclusive theory + statistical power need to be considered.) Confirming/ruling out SM/(C)MFV in Bs,d→μμ requires S-LHCb D physics may well take centre-stage at some point soon. S-LHCb can improve existing mixing/CPV reach by two orders of magnitude. Potential for a few x 10-9 reach in τ→μμμ. More studies needed! 36