No Slide Title · I will interpret my assigned title: ... INFN, Superiore di Sanita', Roma INFN,...

David Hitlin

Caltech

Leith SymposiumDecember 12, 2014

and Science

David Hitlin BABAR and Science Leith Symposium Dec.12, 2014

Une brève histoire de BABAR

I will interpret my assigned title:

“BABAR and Science” to mean that

I can (briefly) tell you about the

formation and early days of the

collaboration: how it came together,

especially David Leith’s role, and a bit

about the physics, in particular, the

measurement of CP violation, and then

tabulate the extraordinary amount of

interesting physics that BABAR has

produced

There is no time to go into any detail on

the prehistory, the history, the design and

construction of the detector, ……

2

The flavor physics situation in the mid ’80’s

In 1981 Carter and Sanda and then Bigi and Sanda showed that a

measurement of CP violation in B0 meson decay to CP eigenstates could

be clearly interpreted in terms of CKM matrix elements, without

theoretical uncertainties due to hadronic structure.

The prospect of a clean measurement in B0 decays was exciting; perhaps

the Standard Model prediction of the strength of CP violation would fail

With the observation in ’83 of a long B meson lifetime by Mark II and

MAC and in ’87 of substantial Bd mixing by ARGUS and UA1, one could

envision measurable CP-violating asymmetries in B0 meson decays

Doing so would require flavor-tagging a B meson and then untangling

mixed from unmixed decays, which could be done using B’s produced in

e+e- annihilation or in hadronic collisions

However, ~107-108 pairs would be needed, a 2 to 3 order-of-

magnitude increase in the then-existing data sample

Exploiting the quantum correlations of pairs produced in ϒ(4S)

decays in e+e- seemed like a particularly elegant approach, but separating

the decays was difficult as the B0 lifetime in the laboratory corresponds

to 19μm


0 0B B

0 0B B

3

The Gold Rush

There were at least 21 e+e- B Factory concepts and proposals (19 ϒ(4S) + 2 Z0)

and several hadronic machine approaches (HERA-B, …….)

Oddone’s concept of using an asymmetric e+e- collider to boost the distance

between the two decay vertices to a measurable regime, implemented in a

multibunch machine stabilized by feedback, was, in the end, the successful approach

Two asymmetric colliders, PEP-II and KEKB, were ultimately built


ϒ(4S)Storage Rings ϒ(4S) Linac-Ring

Collider

ϒ(4S) Recirculating

Linear Collider

Z Factory

Symmetric Asymmetric

PSI (2) APIARY Grosse-Wiesmann Amaldi/Coignet SLC

BINP CITAR JLAB ARES LEP

KEK accumulator PEP-II UCLA

CESR Plus PETRA-II TBA

ISR Tunnel

KEK accumulator

KEK-B

CESR-B

0Z bb

4

The SLAC program in the mid ’80’s looking forward

In the late ’80’s, SLAC’s main project was the SLC (with the Mark II and

SLD detectors)

Laboratories are always searching for their next big project

What was next?

Burt Richter: “We at SLAC believe that “next” for us is a larger scale

[0.5-1.5] linear collider” (ICHEP XXIII Berkeley, July 1986)

[est. 5 years to a proposal]

There was, however, interest in a smaller near term project

SBF (Bloom, Fridman, …) – symmetric, two rings in the PEP tunnel

Apiary (Oddone, Feldman, ….) – asymmetric, small ring on PEP ring

These schemes did not provide sufficient sensitivity to measure

CPV in the B system

Neither went forward

New ideas – SLAC/SLUO Workshops

PEP-II – asymmetric, two rings in the PEP tunnel – CPV capable

t/charm factory (Kirkby, Perl,…)

Charm photoproduction in End Station A (Brau, …)


5

Embedding PEP-II/BABAR at SLAC

The approach to the new accelerator and detector project within SLAC was, of

necessity, different from past practice

PEP-II was to be built by a SLAC/LBNL/LLNL collaboration

The detector was to follow a “CERN model”

David laid the groundwork for this new approach to the detector with a number

of visits to Europe in which he studied in some detail the CERN model, in

particular that employed for the LEP collaborations, and was able to interest the

funding agencies of France, Italy, Germany, the UK and Canada in participating

An important mechanism was the International Finance Committee (c.f. Ian

Corbett’s talk) that managed both the initial investment shares and the ongoing

commissioning and operating costs

The “Common Fund” was a crucial concept

David managed the IFC meetings in his typical skillful manner:

A day of meetings with an “exchange of views”, followed by a good

dinner with adequate liquid refreshment, and a resolution of issues the

next day


6


7


8


9

USA [33/244]California Institute of Technology

UC, Davis

UC, Irvine

UC, Los Angeles

UC, San Diego

UC, Santa Barbara

UC, Santa Cruz

U of Cincinnati

U of Colorado

Colorado State

U of Iowa

Iowa State U

LBNL

LLNL

U of Louisville

U of Maryland

U of Massachusetts, Amherst

MIT

U of Mississippi

Mount Holyoke College

Northern Kentucky U

U of Notre Dame

ORNL/Y-12

U of Pennsylvania

Prairie View A&M

Princeton

Rutgers

SLAC

U of South Carolina

Stanford U

U of Texas at Dallas

Vanderbilt

U of Wisconsin

Canada [7/25]U of British Columbia

Carleton U and CRPP

McGill U

U de Montréal

TRIUMF

U of Victoria

York U

China [4/19]Beijing Glass Research Inst.

Inst. of High Energy Physics, Beijing

Shanghai Inst. of Ceramics (SICCAS)

Tsinghua U, Beijing

France [5/44]LAPP, Annecy

LAL Orsay

LPNHE des Universités Paris 6/7

Ecole Polytechnique

CEA, DAPNIA, CE-Saclay

Germany [1/7]Technische U Dresden

Italy [13/72]INFN, Bari and U di Bari

INFN, Ferrara

Lab. Nazionali di Frascati dell' INFN

INFN, Genova and U di Genova

INFN, Milano and U di Milano

INFN, Napoli and U di Napoli

INFN, Padova

U di Pavia

INFN, Pisa, U di Pisa & Scuola Normale

INFN, Roma and U "La Sapienza"

INFN, Superiore di Sanita', Roma

INFN, Torino and U di Torino

INFN, Trieste and U di Trieste

Norway [1/1]U of Bergen

Russia [2/28]Budker Institute, Novosibirsk

JINR, Dubna

United Kingdom [10/42]U of Bristol

Brunel University

U of Edinburgh

U of Lancaster

U of Liverpool

Imperial College

Queen Mary & Westfield College

Royal Holloway & Bedford New College

U of Manchester

Rutherford Appleton Laboratory

Taiwan [1/3]Academia Sinica

The BABAR Collaboration

10 Countries

77 Institutions

485 CollaboratorsOctober 1995


10

11David Hitlin BABAR and Science Leith Symposium Dec.12, 2014


12

How BABAR got its name

The first use of the name was in 1990, spelled as (not an acronym)

In 1992 the question of copyright was raised and we asked the SLAC™

Business Office to make inquiries

In the Fall of 1993 I wrote to Laurent de Brunhoff extolling the virtues of

CP violation measurements in the meson system and the importance of

investigating the origin of the matter-antimatter asymmetry

He did not answer directly, but in December, 1993 I received a call from Nelvana,

which held the licensing rights to Babar, offering a five year, renewable, royalty-

free license for use of the Babar name and images

The SLAC™ Business Office then concluded a formal agreement

With the new initiative to form a detector collaboration for a detector for

PEP-II it seemed wise to have the new group choose its own name

An email vote was organized, with John Fry as Election Commissioner, and the

name chosen by the proto-Collaboration Council, on May 12, 1994, was BABAR,

with capitalization and relative letter size subsequently decided upon by the

Interim Steering Committee:

\def\babar{\mbox{\slshape B\kern-0.1em{\smaller A}\kern-0.1em B\kern-0.1em{\smaller

A\kern-0.2em R}}}

13

BaBar

BB



14


15

Preparing to do physics – four more workshops


16

Distribution of BABAR physics topics


Topic Papers

CP Violation a 20

CP Violation b 52

CP Violation g 29

B→ charmonium 32

B → open charm 58

B → charmless hadronic 107

B → semileptonic 28

Radiative penguin decays 36

Leptonic decays 11

B mixing and lifetimes 12

D mixing and CP Violation 11

production and decay 10

Charmonium production and decay 14

Charm production and decay 35

Light quark production and decay 19

Tau decays 16

New Physics searches 49

Distribution of BABAR physics topics


Topic Papers

CP Violation a 20

CP Violation b 52

CP Violation g 29

B→ charmonium 32

B → open charm 58

B → charmless hadronic 107

B → semileptonic 28

Radiative penguin decays 36

Leptonic decays 11

B mixing and lifetimes 12

D mixing and CP Violation 11

production and decay 10

Charmonium production and decay 14

Charm production and decay 35

Light quark production and decay 19

Tau decays 16

New Physics searches 49

• After a plenary discussion

at the Padova Collaboration

Meeting in 1997, BABAR

committed to employing

blind analysis techniques,

becoming one of the first

major experiments to do so

• We also pioneered the use

of sophisticated maximum

likelihood and multivariate

techniques that enabled us

to extract maximum

information from the data

in an unbiased manner

CPV-related physics goals

Our initial goal was to measure sin2b, i.e., to find evidence for

CP violation in the interference of mixing and decay in the B meson

system

We then added a series of measurements that allowed us to

overconstrain the Unitarity Triangle

This required measurements of Vub, Vcb, Dmd, and tB,

as well as sin2a and g

We were also able to resolve intrinsic trigonometric ambiguities

We were able to exploit other features of the entangled state

to observe T violation in particle decay

As the data sample increased, it became possible to investigate rare

inclusive and exclusive penguin-dominated decays and to search for

CPV in these decays, in which physics beyond the Standard Model is

most likely to be observable

B0B0


18

The CKM Matrix

d s b

u

c

t

ud us ub

cd cs cb

td ts tb

V V V

V V V

V V V

VCKM = V

udV

ub

* +Vcd

Vcb

* +VtdV

tb

* = 0

There are six unitarity conditions:

only one has elements of comparable size:


19

Wolfenstein: 4 parameters

2 3

2 2

3 2

1 / 2 ( )

1 / 2

(1 ) 1

A i

A

A i A

2 2

1 ... 1 ...2 2

( , ) * *

* *

* *

* *

arg arg

arg arg

td tb cd cb

ud ub td tb

ud ub ts tbs

cd cb cs cb

V V V V

V V V V

V V V V

V V V V

a b

g b

The Unitarity Triangle * * * 0ud ub cd cb td tbV V V V V V

CKMV 4( ) O


20

The unitarity triangle is fully specified by any combination of three

sides and/or angles. If we can measure more than three overconstrained test

The unitarity triangle construction clearly illustrated the overconstrained

Standard Model tests that would be made possible with a measurement

of CP-violating quantities in the B meson system, but which triangle?

The top quark mass was not known.

Dib, Dunietz, Gilman and Nir 1989


21

Measuring CP violation at the

The CP asymmetry is

, 0

, 0

:tag

tag

f B B t

B B t

0

( ) ( )

( ) ( )

sin 2 sin( )

CP

f B

f t f tA

f t f t

m t

are produced at the ϒ(4S) in pairs in a coherent L=1 state0 0B B

Decay + mixing

There are four time distributions : , 0

, 0

tag

tag

f B B t

B B t

sin ( ) cos( )d dB BS m t C m t D D D D


22

eigenstateCP

f CP0 / , ,....S

J K

i

i

i

Measure the and determine the

dilut

mistag fractions

ions

= 1- 2 w

w

D

Determine the resolution function for D z

e+ e-0

tagB

0

recB(4 )S

0

SK

K

Measure D z between BCP and Btag to determine the

signed time difference D t between the decays

zD

Reconstruct exclusive B decays to

CP eigenstates and flavor eigenstates

and tag the flavor of the other B decay

Select events using, primarily,

leptons and 's from hadronic

decays & determine flavor

tagB

K B

B

Overview of the analysis


23

The BABAR Detector

1m

Si Vertex-Tracker, Drift Chamber,

DIRC (Cherenkov), CsI-Calorimeter,

Superconducting Coil, Iron Yoke + RPCs/LSTs


24

Measuring CP violation at the (4 )S


25

An early global CKM Fit


26

Lepton/Photon 2001 Rome

(BABAR)

sin2b

Chronology of

sin2b measurements


27

A current global CKM Fit Consistency of angles

Consistency of angles and

sides from global fit

o4.4

4.2

o

o10

11

89.0

21.1 0.9

68

a

b

g

o

11

12178

a b g

0.026

0.013

0.013

0.014

CKMFitter: 0.131

0.345

UTFit: 0.132 0.023

0.351 0.014


28

Further unitarity triangle tests

CP-violating measurements

Tree-dominated measurements

Loop (mixing)-dominated measurements

All measurements


29

BABAR has been a great adventure for

two decades

We produced results on CP violation

that resulted in the 2008 Nobel Prize

for Kobayashi and Maskawa, as well as

more than 540 papers in refereed

journals

Athough data-taking ended in 2008,

significant results are still emerging


30

The BABAR adventure

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