Olivier Schneider LHCb Upgrade Workshop Edinburgh, January 11–12, 2006 LHCb expected physics performance with 10 fb –1 [email protected] Laboratoire

Olivier Schneider

LHCb Upgrade WorkshopEdinburgh, January 11–12, 2006

LHCb expected physics performance with 10 fb–1

[email protected]

Laboratoire de Physique des Hautes Energies (LPHE)

O. Schneider, Jan 11, 2007LHCb Upgrade Workshop, Edinburgh 2

The whole idea Given the fact that

—LHC will be the facility producing the largest number of b hadrons (of all types), by far, and for a long time

—the Tevatron experiments have demonstrated the feasibility of B physics at hadron machines

perform a dedicated B-physics experiment at the LHC,but with a new challenge:—exploit the huge bb production

in the not-well-known forward region, despite the unfriendly hadronic environment (multiplicity, …) for B physics

• ~ 230 b of bb production in one of the forward peaks (400 mrad),corresponding to nearly 105 b hadrons per secondat a low luminosity of 21032 cm–2s–1

bb angular correlation in pp collisions at s = 14 TeV

(Pythia)

(unchanged since more than a decade)


LHCb spectrometer (before this upgrade workshop)LHCb-1 spectrometer (after this upgrade workshop)

VELO

VELO: Vertex Locator (around interaction point) TT, T1, T2, T3: Tracking stations RICH1-2: Ring Imaging Cherenkov detectorsECAL, HCAL: CalorimetersM1–M5: Muon stations

proton beam

proton beam

Dipolemagnet

1.9 < < 4.9 or 15 < < 300 mrad


LHCb pit (in December 2006)


Pileup and luminosity LHC machine, pp collisions at s = 14 TeV:

—design luminosity = L = 1034 cm–2s–1, bunch crossing rate = 40 MHz—average non-empty bunch crossing rate = f = 30 MHz (in LHCb)—Pileup:

• n = number of inelastic pp interactions occurring in the same bunch crossing• Poisson distribution with mean <n> = Linel/f, with inel = 80 mb• <n> = 25 at 1034 cm–2s–1 not good for B physics

At LHCb:—L tuneable by adjusting final beam focusing—Choose to run at <L> ~ 21032 cm–2s–1

(max. 51032 cm–2s–1)• Clean environment: <n> = 0.5• Less radiation damage • Expected to be available from first physics run

—2 fb–1 of data in 107 s (= nominal year)

pp interactions/crossing

LH

Cb

n=0

n=1


MC studies Technical proposal (1998):

— Rough detector description— No trigger simulation— No pattern recognition in tracking— Parametrized PID performance

Re-opt. Technical Design Report (2003)— Final detector design — Simulation of L0 and L1 trigger only— First version of full pattern recognition

“DC04” MC datasets (2004–2005):— Detailed material description— First simulation of High-Level Trigger

“DC06” MC datasets (2006–2007):— “Final” geometry and material description— Redesigned High-Level Trigger— “Final” reconstruction algorithms

REMINDER of important requirements for B physics

—Flexible and efficient trigger • final states with leptons • fully hadronic final states

—Excellent tracking:• Track finding efficiency• Momentum and mass resolution• Vertexing, proper time resolution

—Particle identification (p/K///e)

Background estimates:– based on a sample of inclusive bb

events equivalent to a few minutes of data taking !

– sometimes can only set limits

Today’s numbers: mostly from DC04 MC, at <L> = 21032 cm–2s–1


VELO

TT

T1 T2 T3 RICH2

RICH1

Magnet

PYTHIA+GEANT full simulation

Expected tracking performance High multiplicity environment:

— In a bb event, ~30 charged particles traverse the whole spectrometer

Track finding:— efficiency > 95%

for long tracks from B decays(~ 4% ghosts for pT > 0.5 GeV/c)

— KS+– reconstruction 75% efficient for decay in the VELO, lower otherwise

Average B-decay track resolutions:— Impact parameter: ~30 m — Momentum: ~0.4%

Typical B resolutions:— Proper time: ~40 fs (essential for Bs physics)— Mass: 8–18 MeV/c2

Mass resolution

Bs 18 MeV/c2

Bs Ds 14 MeV/c2

Bs J/ 16 MeV/c2

Bs J/ 8 MeV/c2

* with J/ mass constraint

*


Particle ID performance Average efficiency:

—K id = 88% mis-id = 3%

Good K/ separation in 2–100 GeV/c range—Low momentum

• kaon tagging —High momentum

• clean separation of the different Bd,shh modes

• will be best performance ever achieved at a hadron collider

invariant mass K invariant mass

With PID With PID

invariant mass

No PID


Flavour tagging

Performance assessed on full MC, after trigger and reconstruction Kaon tags are the most powerful, e.g. opposite K (from bcs) All tags combined with neural network Tagging performance depends on how event is triggered !

— will be measured in data using control channels

Tag D2=(1–2w)2

Opposite 0.7%–1.8%

Opposite e 0.4%–0.6%

Opposite K 1.6%–2.4%

Opposite Qvtx 0.9%–1.3%

Same side (B0) 0.8%–1.0%

Same side K (Bs) 2.7%–3.3%

Combined (B0) 4%–5%

Combined (Bs) 7%–9%

Qvtx

BsB0

D

l-K–

K+PVSV


Trigger performance & rates Algorithms and performance:

—Level-0 trigger algorithms mature, 1 MHz output rate—High-Level Trigger (HLT) under development

• Prototype available within time budget for a limited set of channels

—L0*HLT efficiencies:• Determined using detailed MC simulation

• Typically 30%–80% for offline-selected signal events, depending on channel

HLT output rates:—Indicative rates

(split between streams still to be determined)

—Large inclusive streams to be used to control calibration & systematics (trigger, tracking, PID, tagging)

Output rate

Event type Physics

200 Hz Exclusive B candidates

B (core program)

600 Hz High mass di-muons J/, bJ/X (unbiased)

300 Hz D* candidates Charm

900 Hz Inclusive b (e.g. b) B (data mining)


Physics performance vs L

Rough and quick study:—small DC04 MC samples generated at <L> = 51032 cm–2s–1

for a few representative signal channels—backgrounds not investigated yet (but will be possible with DC06 samples)

Preliminary overall conclusion (for L = 2–51032 cm–2s–1):—Significant gain for dimuon channels

• yield L

—“Statu quo” for hadronic channels • yield ~ constant

—Tagging performance seems ~constant (at least for Bs DsK)

same-side Kopp-side K

vertexelectron

muoncombined

L = 21032

L = 51032


Integrated luminosity scenario 2007 (end):

—Short pilot run at 450 GeV per beam with full detector installed—Establish running procedures, time and space alignment of the detectors—Integrated luminosity for physics ~ 0 fb–1

2008:— LHC reaches design energy—Complete commissioning of detector and trigger at s=14 TeV—Calibration of momentum, energy and particle ID—Start of first physics data taking, assume ~ 0.5 fb–1

2009–:—Stable running, assume ~ 2 fb–1/year

Availability of physics results:—with 0.5 fb–1 in ~2009 —with 2 fb–1 in ~2010—with 10 fb–1 in ~2014


Bs +–

Very rare loop decay, sensitive to new physics:—BR ~3.510–9 in SM,

can be strongly enhanced in SUSY—Current 90% CL limit from CDF+D0

with 1 fb–1 is ~20 times SM Main issue is background rejection

—with limited MC statistics, indication that main background is b, b

—assume background is dominated by b, b LHCb expected performance:

—with 0.5 fb–1: exclude BR values down to SM value—with 2 fb–1: 3 evidence of SM signal—with 10 fb–1: > 5 observation of SM signal


Bs +–

LHCb limit on BR at 90% CL (only bkg is observed)

LHCb sensitivity(signal+bkg is observed)

Integrated luminosity (fb–1)

5 observation

3 evidence

SM prediction

BR

(x1

0–9)

Integrated luminosity (fb–1)

BR

(x1

0–9)

Uncertainty in bkg prediction

Expected final CDF+D0 limit

SM prediction


sin(2) with B0J/KS

Expected to be one of the first CP measurements:—Demonstrate (already with 0.5 fb–1) that we can keep under control the main

ingredients of a CP analysis• in particular tagging extraction from control channels

—Sensitivity (from TDR, improved since):

• ~ 216k signal events/2 fb–1, B/S ~ 0.8 stat(sin(2)) = 0.02

With 10 fb–1:—Should be able to reach (sin(2)) ~ 0.010

• to be compared with 0.017 from final BaBar+Belle statistics

—Can also push further the search for direct CP violating term cos(mdt)

AC

P(t

)

€

ACP(t) =N B 0 → J /ψKS( ) − N B0 → J /ψKS( )

N B 0 → J /ψKS( ) + N B0 → J /ψKS( )

background subtracted, 2 fb–1 (toy MC)


BsDs+ sample and Bs mixing

Measurement of ms:— CDF observed Bs oscillations in 2006:

ms =17.77 ± 0.10 ± 0.07 ps–1 [hep-ex/0609040]compatible with SM

— LHCb expectation with 0.5 fb–1:• ~35k Bs Ds

+ signal events with average t ~ 40 fs and Bbb/S < 0.05 at 90% CL stat(ms) = ± 0.012 ps1, i.e. 0.07%

• will be completely dominated by systematics on proper time scale, but at most ((B0))/(B0) = 0.5%

Importance of BsDs+ sample:

— Normalization channel for all Bs branching fraction measurements• First absolute measurement from Belle, BR(BsDs

+) = (0.68 ±0.22 ±0.16)% [hep-ex/0610003], expect soon ~10% measurement

— Control channel for all time-dependent analyses with Bs decays• Measurement of dilution on cos(mst) and sin(mst) terms

— Important step towards measurement of other Bs mixing parameters • e.g. mixing phase or CP violation in mixing

Reconstructed proper time [ps – 1]

QuickTime™ and aTIFF (LZW) decompressor

are needed to see this picture.Ent

ries

per

0.0

2 ps

Full simulation 0.5 fb–1 (signal only, ms = 20 ps – 1)


Bs mixing phase s with bccs s is the strange counterpart of d=2:

s very small in SM s

SM = –arg(Vts2) =–22 = –0.036 ± 0.003 (CKMfitter)

— Could be much larger if New Physics runs in the box

Golden bccs mode is Bs J/:— Angular analysis needed to separate

CP-even and CP-odd contributions— Expect ~130k Bs J/() signal events/2fb–1

(before tagging), S/Bbb= 8

Add also pure CP modes such as J/(’), c, DsDs — No angular analysis needed, but smaller statistics

Combined sensitivity after 10 fb–1:

— dominated by BsJ/— systematics (tagging, resolution) need to be tackled— hopefully >3 evidence of non-zero s, even if only SM

€

W

€

W

€

b

€

Bs0

⎧ ⎨ ⎪

⎩ ⎪

€

s

€

b€

s

€

⎫ ⎬ ⎪

⎭ ⎪ B s

0

€

t

€

t

QuickTime™ and aTIFF (LZW) decompressor

are needed to see this picture.

Statistical sensitivities on s for 2 fb–1

stat(s) = 0.010 [LHCb-2006-047]


Constraints on New Physics in Bs mixing from s measurement

In April 2006, including CDF’s first measurement

of ms >90% CL

>32% CL>5% CL from hep-ph/0604112

After LHCb measurement of s with (s)= ±0.1(~ 0.2 fb–1)

After LHCb measurement of s with (s)= ±0.1(~ 0.2 fb–1)

After LHCb measurement of s with (s)= ±0.03(~ 2 fb–1)

€

New physics in Bs mixing parametrized with hs and σ s : M12 = 1+ hs exp(2iσ s)( ) M12SM

from hep-ph/0604112

courtesy Z. Ligeti

2009

2009

2010


bsss hadronic penguin decays Time-dependent CP analysis of penguin decays to CP eigenstates

B0 KS:— 800 signal events per 2 fb–1, B/S < 2.4 at 90% CL— After 10 fb–1: stat(sin(2eff)) = 0.14— Similar to a B factory experiment

Bs :

— CP violation < 1% in SM (Vts enters both in mixing and decay amplitudes) significant CP-violating phase NP would be due to New Physics

— Angular analysis required— 4k signal events per 2 fb–1 (if BR=1.410–5), 0.4 < B/S < 2.1 at 90%CL— After 10 fb–1: stat(NP) = 0.042


B0 K*0

s = (m)2 [GeV2]

AFB(s), theory

Sensitivity (ignoring non-resonant K evts for the time being)

—7.7k signal events/2fb–1, Bbb/S = 0.4 ± 0.1—After 10 fb–1:

zero of AFB(s) located to ±0.28 GeV2 determine C7

eff/C9eff with 7% stat error (SM)

Suppressed loop decay, BR ~1.210–6

—Forward-backward asymmetry AFB(s) in the rest-frame is sensitive probe of New Physics:• Predicted zero of AFB(s) depends on Wilson

coefficients C7eff/C9

eff

—Other sensitive observables based on transversity angles are accessible (cf A. Golutvin)

AFB(s), fast MC, 2 fb–1

s = (m)2 [GeV2]


Other rare decays B+ K+l+l– decays

/ee ratio equal to 1 in SM:

—New Physics can have O(10%) effect—After 10 fb–1: stat(RK) = 0.043

Radiative decays:—K*:

• ACP < 1% in SM, up to 40% in SUSY• Can measure at <% level

:• No mixing-induced CP asymmetry in SM,

up to 50% in SUSY :

• Right-handed component of photon polarization O(10%) in SM

• Can get 3 evidence down to 15% (10 fb–1)

Hiller & Krüger, hep-ph/0310219

€

RK = dsdΓ(B → Kμμ)

ds4 mμ

2

q max2

∫ dsdΓ(B → Kee)ds

4 mμ2

q max2

∫ =1.000 ± 0.001

Decay 2 fb–1 yield Bbb/S

B+ K+ 3.8k ~1

B+ K+ee 1.9k ~5

Bd K* 35k < 0.7

Bd 40 < 3.5

Bs 9k < 2.4

b 0.75k < 42

b 4.2k < 10

b 2.5k < 18

b 2.2k < 18


Two tree decays (bc and bu), which interfere via Bs mixing:—can determine s + , hence in a very clean way—similar to 2+ extraction with B0 D*, but with the

advantage that the two decay amplitudes are similar (~3) and that their ratio can be extracted from data

from Bs DsK

Bs Ds–+ background

(with ~ 15 larger BR)suppressed using PID: residual contamination

only ~ 10%

Expect 5400 signal events in 2 fb–1

Bbb/S < 1 at 90% CL

(to be updated soon with DC04 MC)

m = 14 MeV/c2

€

s

€

s

€

b

€

c

€

u

€

s

€

Bs0{

€

}Ds−

€

}K+

€

}K–

€

s

€

s

€

b

€

u

€

c

€

s

€

Bs0{

€

}Ds+


Fit the 4 tagged time-dependent rates:—Extract s + , strong phase

difference , amplitude ratio—Bs Ds also used in the fit

to constrain other parameters (mistag rate, ms, s …)

() ~ 13 with 2 fb–1 —expected to be

statistically limited

from Bs DsK

Both DsK asymmetries 10 fb–1, ms = 20 ps–1)

Ds–K+: info on + ( + s)

Ds+K–: info on – ( + s)


from B± DK±

“ADS+GLW” strategy:—Measure the relative rates of B– DK– and B+ DK+ decays with neutral D’s

observed in final states such as: K–+ and K+–, K–+–+ and K+–+–, K+K–

—These depend on:• Relative magnitude, weak phase and strong phase between B– D0K– and B– D0K–

• Relative magnitudes (known) and strong phases between D0 K–+ and D0 K–+,and between D0 K–+–+ and D0 K–+–+

—Can solve for all unknowns, including the weak phase :

—Use of B± D*K± under study

€

u

€

b

€

u

€

s

€

c

€

u

€

B– ⎧ ⎨ ⎩

€

}D 0

€

}K–

colour-suppressed

€

u

€

u

€

b

€

c

€

u

€

s

€

B–{

€

}D0

€

}K–

colour-allowed

Weak phase difference = Magnitude ratio = rB ~ 0.08

Decay 2 fb–1 yield Bbb/S

B– (K–+)D K– 28k ~0.6

B+ (K+–)D K+ 28k ~0.6

B– (K+–)D K– 180 4.3

B+ (K–+)D K+ 530 1.5

() = 5–15 with 2 fb–1


Treat with same ADS+GLW method—So far used only D decays to K–+, K+–, K+K– and +– final states

from B0 D0K*0

€

}D0

€

d

€

b

€

d

€

s

€

c

€

u

€

B0 ⎧ ⎨ ⎩

€

}K*0

colour-suppressed

Weak phase difference = Magnitude ratio = rB ~ 0.4

€

d

€

b

€

d

€

s

€

u

€

c

€

B0 ⎧ ⎨ ⎩

€

}D 0

€

}K*0

colour-suppressed

Decay mode (+cc) 2 fb–1 yield Bbb/S

B0 (K+–)D K*0 3400 <0.3

B0 (K–+)D K*0 500 <1.7

B0 (K+K–, +–)D K*0 600 <1.4

() = 7–10 with 2 fb–1


Sensitivities to from BDK decays

All channels combined (educated guess): () = 4.2º with 2 fb–1

() = 2.4º with 10 fb–1

B mode D mode Method (), 2 fb–1

B+ DK+ K + KK/ + K3 ADS+GLW 5º–15º

B+ D*K+ K ADS+GLW Under study

B+ DK+ KS Dalitz 8º

B+ DK+ KK 4-body “Dalitz”

15º

B+ DK+ K 4-body “Dalitz”

Under study

B0 DK*0 K + KK + ADS+GLW 7º–10º

B0 DK*0 KS Dalitz Under study

Bs DsK KK tagged, A(t) 13º

Signal only, no accept. effect


Sensitivity to SU(2) analysis of B0 +–, ±0, 00:

—Main LHCb contribution could be B0 00

Time-dependent Dalitz plot analysis of B0 +–0 (Snyder & Quinn)

—14k signal events/2fb–1, B/S ~1

00

–+

+–

average

gen

70 expts superimposed (2fb–1)

2 vs Distribution of fit error

stat() < 10º in 90% of the cases (2 fb–1)

15% (< 1%) fake solutions with 2 (10) fb–1


Impact of LHCb on UT

LHCb (2 fb–1, 10 fb–1):— LHCb: (sin(2)) = 0.02, 0.01 () = 4.2º, 2.4º () = 10º, 4.5º

Lattice QCD (2010, 2014):— 40, 1000 Tflop year ()/ = 2.5%, 1.5%

Central values:— SM assumed

(just for illustration)

%8.1/)(

%6.3/)(

==

10 fb–1 (2014)2 fb–1 (2010)

%9.3/)(

%1.7/)(

==

LHCb + LQCD only

From V. Vagnoni, CKM workshop, Dec 2006


from B and BsKK

Penguin decays, sensitive to New Physics Measure CP asymmetry in each mode:

—Adir and Amix depend on mixing phase, angle , and ratio of penguin to tree amplitudes = d ei

Exploit U-spin symmetry (Fleischer):—Assume d=dKK and =KK —4 measurements and 3 unknowns

(taking mixing phases from other modes) can solve for

With 2 fb–1:—36k B, B/S ~ 0.54

36k BsKK, B/S < 0.14—Sensitivity to Adir and Amix

~ twice better than current world average

€

ACP(t) = Adir cos(Δmt) + Amix sin(Δmt) stat() = 4

If perfect U-spin symmetry assumed

stat() = 7–10 + fake solution

If only 0.8<dKK/d<1.2

assumed

2 fb–1

2 fb–1


Charm physics Foresee dedicated D* trigger:

—Huge sample of D0h+h– decays

—Tag D0 or anti-D0 flavor with sign of pion from D*D0

Performance studies not as detailed as for B physics—just started

Interesting (sensitive to NP) & promising searches/measurements:—Time-dependent D0 mixing with wrong-sign D0K+– decays—Direct CP violation in D0K+K–

• ACP 10–3 in SM, up to 1% (~current limit) with New Physics

• Expect stat(ACP) ~ O(10–3) with 2 fb–1

— D0+–

• BR 10–12 in SM, up to 10–6 (~current limit) with New Physics

• Expect to reach down to ~510–8 with 2 fb–1

Potentially usable statistics in 10 fb–1

D* D0(hh) 500M

D*-tagged D0K+K– from b-hadrons

25M

D*-tagged WS D0K+– from b-hadrons

1M


Summary LHCb can chase New Physics in loop decays:

—couple superb highly-sensitive bs observables• Bs, Bs mixing phase

– expect interesting results with 0.5 fb–1 and 2 fb–1 already– can measure down to SM with 10 fb–1 (in case of no New Physics)

—several other exciting windows of opportunity:• Exclusive b sss Penguin decays (limited, even with 10 fb–1)• Exclusive bsll and bs• B hh Penguins• High statistics charm physics

LHCb can improve significantly on from tree decays:—use together with other UT observables to test CKM even more

But …—this is only MC, performance not demonstrated in real life yet

another 2 years to go !—while thinking about upgrade, please make sure LHCb-1 will work

bs

sb

b s


spares


from BDK Dalitz analyses

B± D(KS+–)K±:—D0 and anti-D0 contributions interfere in Dalitz plot—If good online KS reconstruction: 5k signal events in 2 fb–1, B/S < 1—Assuming signal only and flat acceptance across Dalitz plot:

() = 8 with 2 fb–1

B0 D(KS+–)K*0:—Under study

B± D(KK)K±:—Four-body “Dalitz” analysis—1.7 k signal events in 2 fb–1

—Assuming signal only and flat acceptance across Dalitz plot: () = 15 with 2 fb–1


Unitarity triangle in 2014

%7.1/)(

%5.3/)(

==

%8.2/)(

%8.4/)(

==

Without LHCb With LHCb at 10 fb–1

From V. Vagnoni, CKM workshop, Dec 2006

Documents

Olivier Schneider LHCb Upgrade Workshop Edinburgh, January 11–12, 2006 LHCb expected physics performance with 10 fb –1 [email protected] Laboratoire