# Presentation: 234711

## SuperBaBar Physics Reach

- UT sides
- UT angles
- Rare decays
- Experimental issues
- Stéphane Willocq
- University of Massachusetts, Amherst
- WIN03 Workshop
- Lake Geneva, 6-11 Oct 2003
*Disclaimer:  Many studies are still in progress*
*  **and some are missing*
*Numbers in this talk are not the final word!*

## SLAC B Factory Luminosity Projection

-  Proposed profile: adiabatic PEP-II upgrades until ~2007
-     Super B Factory with peak luminosity of 1036 cm-2 s-1 in  ̧ 2010
- 								  BaBar expected
- 								  integrated lumi
- 								  ~0.6 ab-1 by 2007
- 								  ) 6 108 BB pairs
- 								  SuperBaBar
- 								  integrated lumi
- 								  10 ab-1 per year
- 								  ) 1010 BB pairs/yr
- 								  ~100 x BaBar in
- 								  5 years

_**today**_

- SuperBFactory (SBF)

## CKM Unitarity Triangle

-  Complete test of CKM picture
-    of CP violation will require
-    not only measurements
-    of the angles , , , but
-    also precise measurements
-    of the sides
-   Vcb and Vub:
-   semileptonic decays at e+e-
-   machines
-   Vtd:
-   from B0 oscillation frequency
-   Needs input from Lattice QCD
-   and measurement of ms
-   at hadron machines

## UT Sides:  |Vtd|

-  _BaBar+Belle __**NOW**_:
- md = 0.503 ± 0.007 ps-1
-     uncertainty of 1.4%
-  _BaBar/Belle __**FUTURE**_:
-    Assume 500 fb-1 for each expt
-    Expect total uncertainty of ~0.0023 ps-1, i.e. ~0.5%
-    Completely dominated by systematic uncertainties
-  _Extraction of Vtd: _
-   Needs subtantial improvement from Lattice QCD ( » 15% now)
-   With a measurement of ms  one can reach  » 5% (within a few years)
-   *Note*:	once ms is measured (1-2 yrs? from now), experimental precision in
- 		extracting Vtd is likely to be negligible compared to theory uncertainty

- BaBar
- dilepton

##  Precise measurements of Vub and Vcb
   require a new approach to significantly
   reduce systematic (theory) uncertainties
 “B beam” technique:
	Fully reconstruct one of the two B mesons
	Reconstruct hadronic decay B ! D(*) (n1§ n2K§ n3K0S n40)
	Breco efficiency = 0.3% for B0B0 and 0.5% for B+B- events (BaBar)
	For 10 ab-1, this yields ~1010 BB ! 15 x 106 B0B0 reco 
                                                                  25 x 106 B+B- reco
	! ~40 million B mesons recoiling against fully reconstructed B
  ) Full kinematical constraints available
  ) Separates decay products from the two B mesons & suppresses bkgd
  ) Provides B flavor tag
  B beam technique is ideal for inclusive measurements of
  semileptonic branching fractions ! Vcb and Vub
  Technique expanded with semil. decays and partially reconstructed decays

-    require a new approach to significantly
-    reduce systematic (theory) uncertainties
-  “B beam” technique:
- 	Fully reconstruct one of the two B mesons
- 	Reconstruct hadronic decay B ! D(*) (n1§ n2K§ n3K0S n40)
- 	Breco efficiency = 0.3% for B0B0 and 0.5% for B+B- events (BaBar)
- 	For 10 ab-1, this yields ~1010 BB ! 15 x 106 B0B0 reco
-                                                                   25 x 106 B+B- reco
- 	! ~40 million B mesons recoiling against fully reconstructed B
-   ) Full kinematical constraints available
-   ) Separates decay products from the two B mesons & suppresses bkgd
-   ) Provides B flavor tag
-   B beam technique is ideal for inclusive measurements of
-   semileptonic branching fractions ! Vcb and Vub
-   Technique expanded with semil. decays and partially reconstructed decays

**Vub, Vcb: B-Beam Technique**

## Semileptonic decays

-   Inclusive semileptonic decays:
-     b ! u l  with B beam technique ) high S/B at low hadronic mass mX
-     BaBar (82 fb-1):
-    Theory uncertainty can be reduced
-    to ~5% by cutting on both mX and q2
-    but overall uncertainty saturates at 6%
-    for lumi  ̧ 2 ab-1
- 						Further reduction of theory possible					if mb and Fermi motion effects
- 						constrained from data

## Measurements of UT angles

-  Projections based on current analyses at BaBar
-    ! Uncertainties are mostly statistical and will continue to improve
-         as the sample size increases
-    ! Only exception may be for sin(2) in B0 ! J/ K0s  for which it may be
-        necessary to use only lepton tags to reduce systematic uncertainty

-  syst

-  syst lepton
- tags (~70%
- larger  stat if
- only lepton tags
- used)

-  stat for sin2
- meas.

## UT angles systematics

**Main systematic uncertainties in time-dependent asymmetries**
- 1. ___t resolution_: uncertainties due to vtx detector misalignment and
-     beam spot position ! reduce with improved understanding of detector
- 2. _Dilutions_: uncertainties due to difference between flavor-tagged sample
-     and charmonium event sample ! only slight improvement
- 3. _Background_: uncertainties in background composition and asymmetry
-     ! sideband data will provide much tighter constraints than currently used
- 4. _MC correction_: improves with increased MC statistics
- projected
- (syst) for sin 2
- measurements

- lepton tags only
- 50 ab-1

## Measurements of sin2

-  Compare trees and loops (penguins) in clean modes
- WAvg:     0.736 § 0.049                                           -0.14 § 0.33
-  B0 !  K0s provides excellent window into new physics
-    & current data leaves room for new physics in b ! s transitions
- ) but low rates due to BF(B0 !  K0s) / BF(B0 ! J/ K0s)  » 10-2
- ) need very large data samples
- 10 ab-1:     (sin2) < 0.01  [J/ K0s]                        (sin2) » 0.05   [ K0s]
- SuperBaBar could see  ̧ 5 deviation from J/ K0s of  ̧ 33% with 10 ab-1
-                                                                                         ̧ 15% with 50 ab-1

## Measurements of (I)

**Measurements of ********(I)**

-  Measurement of time-dependent CP asymmetry in B0 ! +- :
-                                                                                                    BaBar (113 fb-1)
-    ) *stat*(S) = 0.023  for 10 ab-1
-    *but* penguin pollution can be sizeable:
-   		 2eff = 2 + 
-    ) need to measure BF(B0 ! 00),
-         BF(B0 ! 00) and determine 
-         via isospin analysis
-    ! e+e- machines ideally suited for this

## Measurements of (II)

-  Toy MC study of isospin analysis in B ! :
-    Several choices of BF were studied
-    For example, results using
- 	BF(B0 ! 00) = 1.5 x 10-6
- 	BF(B0 ! 00) = 0.5 x 10-6
-                                                                               4-fold ambiguity!

- = 4 to 10

- 

- ) really need Super B Factory luminosities for precise and clean
-      determination of !

- toy MC
- expts RMS

- 4-fold amb.
- not included

## Measurements of (I)

| 2 ab-1 |  |  |
| --- | --- | --- |
| r | sin2 |  |
| 0.3 |  |  |
| 0.2 |  |  |
| 0.1 | unreliable | unreliable |

- Crucially depends on r (breaks down for  r < 0.1?)
- 8-fold ambiguity spoils the extraction of 
- But ***A******CP ******= 2r *****sin ************** sin ********  is **accessible**:      ****(*A**CP*) ~ **0.03** with 2 ab-1

- Gronau-Wyler-London method: B ! D0 K
- with D0 decays to CP even and odd final states

## Measurements of (II)

**Measurements of ********(II)**

-  600 fb-1:  toy MC study (A.Soffer)
-    Combines GWL and ADS methods
-    and uses all D(¤)K(¤) final states
-    ! 8-fold ambiguity!
-  10 ab-1:  ambiguities can be resolved once
-    sensitivity is high enough (at Super B Factory)
-    Too early to give firm projection
-    but expect B ! D(¤)K(¤) studies to determine
-     with a statistical uncertainty of 1o to 2.5o
-    (for 10 ab-1)
-  _**sin(2**__****__**+**__****__**)**_ from B0 ! D(¤)  /  / a1 / K0s
-    main uncertainty in the ratio between
-    “Vub” and “Vcb” amplitudes
-    ) expect uncertainty of 0.05 for 10 ab-1

## Radiative Penguin Decays (I)

-  _UT side measurement with __**exclusive**__ decays_:
-    Measure BF(B    ) » 1 x 10-6  to extract |Vtd / Vts| via
-    ! BaBar 500 fb-1:  Uncertainty in  |Vtd / Vts| of 10-15%   [(theory)  » 15%]
-         Complementary to ms / md (but remember sin 2 in  K0s !)
-     !  ̧ 10 fb-1:   Limited by » 5% systematic uncertainty + theory » 10%?
-  _UT side measurement with __**inclusive**__ decays_:
-    BF(B   Xd ) / BF*** ***(B   Xs )  yields cleaner  |Vtd / Vts|     [(theory) <10%?]
-    but inclusive B   Xd  decays are very difficult experimentally
-    may be possible with >10 ab-1 and B-beam technique
-    Study with lepton tag (to suppress udsc bkgd) yields
-    stat on |Vtd / Vts|  of 15-20% for 10 ab-1 and 10-15% for 50 ab-1

## Rare semileptonic decays (I)

**Rare semileptonic decays (I)**

-  Decays involving b  s l+ l- transitions
- are sensitive to new physics contributions

- SUGRA

- SM

- MIA-SUSY

- SM

- B ! K¤ + - decay rate

- B ! K¤ + - forward-backward asymmetry

- [M(l+ l-)]2

- MIA-SUSY C10 > 0

- MIA-SUSY C7 > 0

- SUGRA C7 > 0

## Rare semileptonic decays (II)

-  _Semi-inclusive analysis_: B ! Xs l+ l- decays
-    BF theory  ~15%  for all ŝ = mll2/mb2
-    [6% scale only T.Hurth] (11% U. Haisch)
-                   for 0.05 < ŝ < 0.25
-     Expect ~350 signal events for 0.5 fb-1
-                ~7000 signal events for 10 ab-1
-     Estimate for BF measurement uncertainties:
-   ) Need Super B Factory to reach (future) theory uncertainty at low ŝ

- BaBar 82 fb-1

| Signal yield
Xs e+e+ Xs +  |        500 fb-1 |       1000 fb-1 |        10 ab-1 |        50 ab-1   |
| --- | --- | --- | --- | --- |
| All ŝ (exc. J/veto) |          stat = 10%
7% <syst < 14% | stat = 7%
5% <syst < 14% | stat = 2.1%
1.5% <syst < 6%? | stat = 1.0%
0.7% <syst < 6%? |
| 0.05 < ŝ < 0.25 |   stat = 16% |    stat = 11% |     stat = 3.4% | stat = 1.5% |
| ŝ > 0.65 |    stat = 22% |    stat = 15% |     stat = 5.0% |     stat = 2.3% |

## Rare semileptonic decays (III)

-  _Forward-backward asymmetry_ in B ! Xs l+ l-
-   In dilepton rest frame:
-   NF = # l+ along b-quark direction
-   NB = # l+ opposite b-quark dir.
-   Predicted zero point of the asymmetry:
-   AFB = 0 for ŝ = ŝ0 = 0.162 § 0.008 (NNLL)
-   Estimate with 10 ab-1 sample (after bkg subtraction)
-    ! ŝ0 ' 0.14 § 0.04(stat)
-    Estimate for asymmetry measurement (stat only):
-     ) AFB clearly needs high-luminosity B Factory

- pure signal 10 ab-1

*A**FB*

| AFB 
Xs e+e+ Xs +  |      500 fb-1 |     1000 fb-1 |      10 ab-1 |     50 ab-1   |
| --- | --- | --- | --- | --- |
| ŝ < ŝ0 |    -0.02 ± 0.17 |  -0.02 ± 0.12 |   -0.017 ± 0.039 | -0.017 ± 0.017 |
| ŝ > ŝ0 |     0.17 ± 0.22 |   0.17 ± 0.16 |    0.173 ± 0.050 |  0.173 ± 0.022 |

## Rare semileptonic decays (IV)

-  _Exclusive analysis_: B ! K(¤) l+ l- decays
-    Based on current BaBar analysis,
-    expect # signal events for 10 ab-1 of
-    2000 for K e+ e- and 1500 for K + -
-    2600 for K¤ e+ e- and 1700 for K¤ + -
-    Current theory uncertainty in BF is ~34%
-    ) main interest is in the forward-backward asymmetry
-         (coming soon...)

- K l+ l-

- K¤ l+ l-

- BaBar 113 fb-1

## Other Measurements

-  Many other physics topics become very interesting at Super B Factory
-    luminosities, for example:
**Rare B decay processes with missing particles**: B !  , K, , ! method like full (or partial) B-beam technique is crucial
**Radiative penguin B decays**: reduced theory dependence inBF measurement of inclusive b ! s   (full or partial B-beam technique)	tot ~7% (0.5 ab-1) and ~2% (10 ab-1)Interesting level of sensitivity for ACP measurements
**Charm physics**: huge samples for D0 mixing (x~0.001)and rare D decay studies
**Tau physics**: sensitivity for lepton-number violationin  !    (expect 5 sensitivity down to BF of 1 x 10-7)
- Other ideas...

## Super B Factory Parameters

-  How do we get a factor of 100 improvement in luminosity?
-                                                  Super B Factory                        B Factory

| Beam | e+ | e- |  | e- | e+ |  |
| --- | --- | --- | --- | --- | --- | --- |
| E (GeV) | 8.0 | 3.5 |  | 9.0 | 3.1 |  |
| #bunches                | 7000 |  |  | 800 |  |  |
| lifetime (min) | 7 |  | 5 | 200 |  |  |
| Current (A) | 10.3 |  | 23.5 | 1.0 |  | 1.8 |
| * (mm) | x=150/y=1.5 |  |  | x=450/y=10 |  |  |
| Emittance (nm) | x= 44/y=0.44 |  |  | 40/2.5 |  |  |
| Beam spot (m) | x= 81/y=0.8 |  |  | x= 147/y=5 |  |  |
| Tune shift | 0.10 |  |  | 0.07 |  |  |

## Super B Factory Environment

-  Reaching 1036 implies that a series of issues have to be faced:
- 	►Higher beam currents, stronger focusing, *continuous injection*
- 	►Increased background and higher rates for detector
- 		) Radiation damage
- 		) High occupancy

- SVT Dose

- SVT Hardness

- 7 Mrad/yr

- DCH Occupancy

- >100% Occupancy

- ) NEED NEW DETECTOR

## Super BaBar Detector

-  Possible upgrade of BaBar detector:
-   Emphasis on high segmentation, fast integration time, radiation hardness

- IFR upgraded (ongoing)
- Remove SVT,DCH, EMC, DIRC
- New EMC – liquid Xe
- New tracker- Two inner pixel
-      layers- Seven(?) thin   double-sided   Si-strip arch layers
- New DIRC(s) with compact readout

## Detector Issues

-  Super BaBar detector designed to have sufficient granularity to
-    deal with the high occupancy
-    However, some issues need investigating...
- 	►tracking efficiency and fake tracks
- 	►calorimeter resolution, fake photons, ability to veto pi0, etc...
- 	►particle ID performance
- 	►etc...
*   **!** studies yet to be performed*
-  Some *detector R&D is needed* for:
-   	►thin (100 m) Si detector and low-power electronics
- 	►small-cell drift chamber in high radiation environment
- 	►focusing DIRC with pixelated PMT
- 	►choice of EM calorimeter: liquid Xe vs. (fast) crystals
- 	►technology for muon ID

## Summary

- A high-luminosity B Factory promises samples of up to 1011 B mesons (5 yrs)
- Huge range of
- physics but
- motivation is
- discovery/
- measurement
- of new physics
- via
**CPV and**
**rare decays**
- (many extremely
-  interesting topics
-  and analyses not
-  shown!)

|  | BaBar (2007) |  | SuperBaBar (2012) |  |
| --- | --- | --- | --- | --- |
| Lumi | 600 fb-1 |  | 10 ab-1 |  |
|  | stat | syst  | stat | syst |
|  sin2eff () | 0.095 | 0.02-0.03 | 0.023 | 0.01-0.02(?) |
|  sin2eff () | 0.078 | 0.02-0.03 | 0.019 | 0.01-0.02 |
| BF(B0!00) | 12% | <10% | 3% | ? |
| (Bd ! DK) |  |   | 1.0o-2.5o |  |
|  sin(2 +) | 0.2 |  | 0.05 |  |
|  sin(2)  K | 0.19 | 0.03 | 0.046 | 0.01-0.02 |
| BF(B!Xsl+l-) | 10% | ~10% | 2% | ~4% |

- Current knowledge (subject to change...)

## Additional Slides

## BTeV / Super B Comparison  (D.Hitlin)

| Mode |          BTeV |  |         Super B |  |
| --- | --- | --- | --- | --- |
|  |  Yield | Tagged | Yield | Tagged |
| BsJ/ | 12650 |   1645    |    - |     - |
| B-K- | 11000 | 11000 |   14000 |   14000 |
| B0Ks |   2000 |     200 |   5000 |     1500 |
| B0K*+-   |   2530 |   2530 |   ~1000 |   ~1000 |
| Bs +-  |         6 |      0.7 |       - |      |
| B0+-   |         1 |      0.1 |       0 |        - |
| D*++D0,  D0K-+ |   ~108 |   ~108 | 1.6x107 | 1.6x107 |

- 1-year yields

## BTeV / Super B Comparison  (D.Hitlin)

- Number of flavor tagged *B*0***+ **** -* (*B*=0.45x10-5)
- Number of *B**-* *D*0 ** (Full product *B*=1.7x10-7)
*B**s* , *B**c* and b studies are not done at **(4*S*) *e**+**e**-* machines

## Snowmass 2001 E2 Group Comparison

## UT Angles: Impact of SUSY

-  Integrated luminosity:

**r**

**r**

**r**

- MSSM phase

- SM phase

- Ratio of amplitudes in SM

- Ratio of MSSM/SM amplitudes

## Precision on the determination of UT sides

-  Snowmass 2001 projections:
-   * best approach with ms/md but could also check with   / K* 

| CKM | Analysis | stat
(2007)% | stat
(2012)% | sys
(2012)% | th
(>2010) % |
| --- | --- | --- | --- | --- | --- |
| Vcb | D(*,**)l | 0.4 | 0.1 | 1 | 1 |
|  | b cl | 1 | 0.5 | 0.5 | 5 |
| Vub | bul | 3 | 0.7 | 2.5 | 5 |
|  | B Xul | 9 | 2 | 2.5 | 5 |
| Vtd
 | Md* | 0.2 | 0.05 | 0.5 | 5 |
| Vub,Vtd | B |  | seen?! |  |  |