1 1 D. Hitlin Super B Factory Trigger Workshop Dec. 2/3, 2004 David Hitlin Caltech December 3, 2004

B abar ™ and © L. de B runhoff

1D. Hitlin Super B Factory Trigger WorkshopD. Hitlin Super B Factory Trigger Workshop Dec. 2/3, 2004Dec. 2/3, 2004 11

David HitlinDavid HitlinCaltechCaltech

December 3, 2004December 3, 2004



Physics objectives of a Super B Factory

The physics objectives of an experiment at a Super B Factoryrevolve around the search for New Physics. The specific approaches fall into several distinct categories

Improvements in the classic unitarity triangle-related measurementsto the “ultimate” precision [a balance of theoretical, statistical and systematic uncertainties]

UT angles measure asymmetries with minimum systematic error

lepton tag has smallest systematicsMeasure branching ratios of rare modes for

UT sidesuse the recoil method to reduce backgrounds and theoretical uncertainties

Maximum sensitivity for very rare decays – B, D, Branching fractionsACP, AFB

Kinematic distributions



The recoil physics method at the(4S)

• Fully reconstruct one of the two B’s in hadronic modes (for some topics, in semileptonic modes as well)• …and do it with “high” efficiency• The rest of the event is the other B, whose four-momentum is known

You have a single B beam, withreduced systematics in Vcb, Vubub studies, and

reduced backgrounds for rare decays, especially those involving neutrinos or photons

e-DD**

e+

BBrecoreco

BBrecoilrecoil

Xu

Semileptonic decaysB D(*)B ()BXc,u…… )B D(*)sensitive to New PhysicsB D(*)

Purely leptonic decays B….B KB invisible

B Xs



Measurement precision – angles of the Unitarity Triangle

Unitarity Triangle - Angles e+e- Precision 1 Year Precision

Measurement 3/ab 10/ab 50/ab LHCb BTeV

SBR’s isospin) 6.7 3.9 2.1

() (Isospin, Dalitz) (syst 3) 3, 2.3 1.6, 1.3 1, 0.6 2.5 -5 4

() (penguin, isospin) (stat+syst) 2.9 1.5 0.72

(J/ KS) (all modes) 0.3 0.17 0.09 0.57 0.49

(BD(*)K) (ADS) 2-3 ~10 <13

(all methods) 1.2-2

Theory: ~5%, ~ 1% ~0.1%



Probes of new physics - I

1) Measure the CP asymmetry in modes other than that measure sin2 in the Standard Model

Precision of benchmark sin2 in can improve to the 1% levelExpect the same value for “sin2 ” in “but different SUSY models can produce different asymmetriesA great deal of luminosity is required to make these measurements to meaningful precision

0 0/ SB J Ky®

, ,b ccs b ccd b sss® ® ®

0 0/ SB J Ky®

* *2

* *( 1) itb td cb cs

treetb td cb cs

q A V V V Ve

p A V V V Vbl h -= = = -

* *2

* *( 1) itb td tb ts

penguintb td tb ts

q A V V V Ve

p A V V V Vbl h -= = = -

0 0SB Kf®

0 0/ SB J Ky®



Extrapolated statistical errors on CP asymmetries

10 to 50 ab-1 are required for a meaningful comparison

Currentprecision

BABAR measurement errors



Measurement precision – rare decays

Rare Decays – New Physics e+e- Precision 1 Year Precision

Measurement Goal 3/ab 10/ab 50/ab LHCb BTeV

bd / (bs - -

BD(*)) SM: : 8x10-3 10.2% 5.6% 2.5% - -

Bs) (K-,0, K*-,0)

1 exclusive mode: ~4x10-6

~3 - -

Binvisible) <2x10-6 <1x10-6 <4x10-7 - -

Bd ) - - 1-2 1-2

Bd ) - - - -

) <10-8 - -



Rare Decays – New Physics – CPV e+e- Precision 1 Year Precision


S(B0KS) SM: <0.25% 16% 8.7% 3.9% 16 ?? 7 ??

S(B0KS+KL) SM: <0.25% - -

S(B'Ks )SM: <0.3% 5.7% 3% 1% - -

S(BKs) SM: <0.2% 8.2% 5% 4% (?) - -

S(BKs) SM: <0.1% 11.4% 6% 4% (?) - -

ACP (bs SM: <0.5% 2.4% 1% 0.5% (?) - -

ACP(BK*) SM: <0.5% 0.59% 0.32% 0.14% - -

CPV in mixing (|q/p|) <0.6% - -

Measurement precision - rare B decays



Rare Decays – New Physics e+e- Precision 1 Year Precision


bd / (bs - -

BD(*)) SM: : 8x10-3 10.2% 5.6% 2.5% - -

Bs) (K-,0, K*-,0)

1 exclusive mode: ~4x10-6

~3 - -

Binvisible) <2x10-6 <1x10-6 <4x10-7 - -

Bd ) - - 1-2 1-2

Bd ) - - - -

) <10-8 - -

Measurement precision – rare decays

Masiero, Vempati, Vives

is sensitive to 23 generation mass insertions,(analogous to b sss) but in the lepton sector



Mass insertion approximation: model-independent

KS BABAR (now)

KS 30 ab-1

The scale of New Physics

Ciuchini, Franco, Martinelli, Masiero, & Silvestrini

23 mass insertion13 mass insertion

ACP (J/ KS-0KS) ACP (J/ KS-KS)



Physics demands an open trigger

In the face of the impressive rates and amounts of data that will be encountered at a Super B Factory, the first reaction is usually to think about a restrictive triggerThis is unlikely to work, since the physics requires

A large, unbiased sample of fully reconstructed B decays

Recoil studies, ACP, B to invisible, etc.

Sensitivity to rare decays

A trigger that can do this will manifestly provide a large sampleof D decays as well



The “Snowmass Year” was defined in 1988, based on data from CESR/CLEO:

1 Snowmass Year = 107 s

The Snowmass Year factor is meant to account forThe difference between peak and average luminosityAccelerator and detector uptimeDeadtime………………………..

PEP-II performance April 2003-April 2004 (Dec 03 Trickle LER, Feb 04 Trickle HER)

Given the excellent performance of PEP-II/BABAR and KEK-B/Belle, and the advent of trickle injection, the modern B factory Snowmass Year constant is 1.4 x 107

Thus we can integrate 10 ab-1/year with 7 x 1035cm-2s-1, instead of with 1036cm-2s-1

The New Snowmass Year

2 1PEAK

1Year

(cm s ) SnowmassYear (s)dt - -= ´ò e eL L



Occupancy extrapolations are uncertain, but sobering

2x10

35

7x10

35

10

36

20%

2x10

35

7x10

35

10

36

Now: 8 physics clusters



Tracking will have to be done with silicon, not gas

We will have to develop a silicon tracking trigger



Top module

SVT Occupancy (Top)

0

40

80

120

160

200

240

8 200 700 1000Luminosity (10E33)

Oc

cu

pa

nc

y (

%)

100%

50%

20%

10%

0%

Lumi term

DANGER with 4x granularity increase



Bottom module

SVT Occupancy (Bottom)

0

40

80

120

160

200

240

8 200 700 1000Luminosity (10E33)

Oc

cu

pa

nc

y (

%)

100%

50%

20%

10%

0%

Lumi term




Midplane module

SVT Occupancy (Midplane)

0

40

80

120

160

200

240

8 200 700 1000

Luminosity (10E33)

Occ

up

ancy

(%

)

100%

50%

20%

10%

0%

Lumi term


574%



There will be pixels, (striplets) and DSSD layers

Pixel or striplets (2 layers)

Intermediate DSSD(3 layers)

Central Silicon Tracker(4 layers)R(outer) = 60 cm



There is a fast, rad hard replacement crystal for CsI(Tl)



Comparison of CsI(Tl), LSO, Liquid Xe

CsI(Tl) LSO LXe

Atomic number Z 54 effective 65 effective 54

Atomic weight A 131

Density (g/cc) 4.53 7.40 2.953

Radiation length (cm) 1.85 1.14 2.87

Molière radius (cm) 3.8 2.3 5.71

scint (nm) 550 420 175

scint (ns) 680, 3340 47 4.2, 22, 45

Light yield (photons/MeV) 56,000 (64:36) 27,000 75,000

Refractive index 1.8 1.82 1.57

Liquid/gas density ratio 519

Boiling point at 1 atmosphere (K)

165

Radiation hardness (Mrad) 0.01 100 -

Cost/cc 3.2 >7 (50 ???) 2.5





An upgrade path from BABAR to SuperBABAR

BABAR

SuperBABAR

DRIFTCHAMBE RCABLES

- +

SOLENOID

SI LICONTR ACKER

INST RUMENTEDFL UX RETURN

R

DIRC

LXe EMC SVT 5 layers of double-sided striplets 2 layers of thin pixels + 3 layers of thin pixels

Tracker 4 layers of thin double-sided Si

EMC Liquid Xe scintillation or fast, rad-hard crystals (LYSO)

+ New trigger and DAQ system

DIRC Faster, pixelated readout



Projections depend heavily on the luminosity term

Cross sections:BB: 1 nb 1010 BB pairs/yearuds: 1.6 nb, c: 1 nbleptons (): 0.78 eachrecognizable Bhabhas: ~50nb

The Level 1 trigger rate:BABAR/PEP-II projections show that the hardware trigger rate will be dominated by luminosity-related interactions at luminosities above 1034 .At 7x1035, this gives a rate for a BABAR-like hardware trigger of about 50K events per second. Half of these are scaled Bhabhas. There are ~ 6K beam background-like events per second.

Unless we are clever we might have to cope with a ~100K/second L1 rate !Event size ~50K (~2X BABAR)

How well must we know the efficiency of each trigger line?Precise absolute branching ratios may not be of extreme importance

Scaled from GPDF in Hawaii



The challenge

Design a trigger D/A system with a silicon tracking plus fast calorimeter trigger which has all the virtues of a classical e+e- trigger in a much more challenging environmentStore and analyze the data efficientlyFind New Physics

Documents

1 1 D. Hitlin Super B Factory Trigger Workshop Dec. 2/3, 2004 David Hitlin Caltech December 3, 2004