David Hitlin Caltech Let’s Celebrate Jonathan July 24, 2008

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Babar ™ and © L. De Brunhoff

David HitlinCaltech

Let’s Celebrate Jonathan

July 24, 2008

CP Violationand

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David Hitlin "Let's Celebrate Jonathan" July 24, 2008

B abar ™ and © N e lvana

3 3L. De Brunhoff

BABAR was a great adventure for two decades, now nearly concluded This day, devoted to highlighting Jonathan Dorfan’s many contributions,

is, of course, a most appropriate one to look back on BABAR and its accomplishments

Jonathan served as head of the PEP-II project and as BABAR ‘s Technical Coordinator, succeeding Vera Lüth

His leadership in these endeavors, as in many others, was characterized by his skill, drive, understanding of people, deal-making ability and his ability to keep his eye on the ball

The latter is perhaps best characterized by the BABAR/PEP-II mantra:

“What is the effect of ……….. on the measurement of sin2b ?”,

where ………….. could be degree of mode suppression in the RF cavities gauge of magnet power supply cables length of the CsI(Tl) crystals thickness of the drift chamber end plates or any of a thousand other decisions we had to make



4 4L. De Brunhoff

CP violation and baryogenesis

The experimental study of CP violation dates back to 1964, when Christensen, Cronin, Fitch and Turlay discovered that the decays of KL

mesons violate CP invariance by ~2 parts per thousand In 1967 Andrei Sakharov showed the connection between CP violation

and the dominance of matter over antimatter in the universe In the Big Bang there was, by assumption, an equal amount of matter

and antimatter in the universe (i.e., the net baryon number of the universe was zero), but we now live in a matter universe

The Sakharov conditions for the disappearance of the antimatter: Violation of C and CP symmetry – observed, allowed in the Standard Model Baryon number-violating interactions - beyond the Standard Model Departure from thermal equilibrium (an “arrow of time”) - inflation


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Well up above the tropostrata There is a region stark and stellar Where, on a streak of anti-matter Lived Dr Edward Anti-Teller.

Remote from Fusion's origin, He lived unguessed and unawares With all his antikith and kin, And kept macassars on his chairs.

One morning, idling by the sea, He spied a tin of monstrous girth That bore three letters: A. E. C. Out stepped a visitor from Earth.

Then, shouting gladly o'er the sands, Met two who in their alien ways Were like as gentils. Their right hands

Clasped, and the rest was gamma rays. The New Yorker, 1955

ERDA DOE

Perils of Modern Living Harold P. Furth



6 6L. De Brunhoff

CP violation and baryogenesis

The annihilation of matter and antimatter in the very early universe was nearly complete: only a tiny fraction of the baryons escaped annihilation:

A quantitative measure of the process at early times is provided by the ratio of baryons to relic photons in the cosmic microwave background

nbaryons/nphotons = (5.1 +0.3-0.2)x10 –10

The baryons that escaped annihilation were those that could not find a an antiparticle partner, the partner having preferentially decayed due to CP violation in the weak interaction

However, the expected Standard Model scale of CP violation is far too small to produce this many baryons. At best, the Standard Model can produce

nbaryons/nphotons ~ 10 –20

Getting a clear handle on the precise strength of CP violation in KL decay was hard

because KL mesons are so light, it is difficult to connect the CP asymmetry measured at the meson level with the underlying strength at the quark level



7 7L. De Brunhoff


8 8L. De Brunhoff

The situation in the mid ’80’s

In 1981 Bigi and Sanda showed that a measurement of CP violation in B0 meson decay to CP eigenstates could be clearly interpreted, without theoretical uncertainties.

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

contemplate measuring 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, at least 107-108 B pairs would be needed, a 2-3 order of

magnitude increase in the 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



9 9L. De Brunhoff

The Gold Rush

This led to 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 o an measurable regime was, in the end, the most successful approach

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

ϒ(4S) Storage Ringsϒ(4S) Linac-Ring

Collider ϒ(4S) Recirculating

Linear ColliderZ Factory

Symmetric Asymmetric

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

Novosibirsk CITAR JLAB ARES LEP

KEK accumulator PETRA-II UCLA

CESR Plus PEP-II TBA

ISR Tunnel

KEK accumulator

KEK-B

CESR-B

0Z bb


1010


The ¡ resonances in e+e- annihilation: non-relativistic atomic systems

Mϒ(4s) = 10.5794 + 0.0012 GeV

G¡(4s) = 20.5 + 2.5 MeV

0 0

The (4 ) decays to

, in acoherent =1 state

S

B B B BL

+ -

bb

A practical application of EPR



11 11L. De Brunhoff

Motivation for B0 meson CP Violation measurements

Since CP violation is a necessary ingredient to produce a baryon asymmetry, and since the theoretical strength of CP violation in the three generation Standard Model is numerically insufficient to produce the observed asymmetry, it was hoped that a measurement of a CP-violating asymmetry that could be unambiguously related to the Standard Model CP phase would produce a surprise

The result was that the Standard Model phase produces exactly the needed amount of CP violation for B meson decays to pass the overconstrained Unitarity Triangle tests

Thus at this point, experimentally the Standard Model does not have the strength of CP violation to produce the observed baryon asymmetry

How do we measure the strength of CP violation in the Standard Model?



12 12L. De Brunhoff

| |V Vc d c b

V tdV ub*

The B Unitarity Triangle

0*** tbtdcbcdubud VVVVVV*

*td tb

cd cb

V V

V V*

*

ud ub

cd cb

V V

V V

1

* * *

* * *arg arg argtd tb cd cb ud ub

ud ub td tb cd cb

V V V V V V

V V V V V Va b g

æ ö æ ö æ ö÷ ÷ ÷ç ç çº - º - º -÷ ÷ ÷ç ç ç÷ ÷ ÷ç ç ç÷ ÷ ÷ç ç çè ø è ø è ø

b ccs®b ddd®

b uud®

0 0/d SB J Ky®0 0s SB Kr®

0dB p p+ -®


The CKM matrix describing the transitions among the three quark generations is unitary

There are six unitarity relations The most useful unitarity condition is:

The sides of the unitarity triangle are determined by

measurements of the magnitudes of CKM matrix elements CP-violating asymmetries in B0 decays to CP eigenstates

measure the angles of the unitarity triangle, thereby providing an overconstrained situation and thereby a unique test of the Standard Model in the CKM sector


13 13L. De Brunhoff


0 0 0 0Interference between J/ ( ) and J/ ( )

decays allows determination of sin2S SB K b ccs B K b ccs

y y

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To measure a phase, you need interference of two amplitudes

2

1 2

1 2 1 2 1 2

( )

( ) ( ) 4 sin( )sin( )

P i f A A

P i f P i f A A

CP violation can arise due to interference between two amplitudes with different phases - a weak phase f that changes sign under CP and a strong phase d that is invariant under CP

.

i f CP f

A1 = | A1| e i1 e -

i1

A2 = | A2| e i2 e i

2 A2 = | A2| e i2 e -

i2

i

A1 = | A1| e i1 e i

1


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The Unitarity Triangle in 1990

Dib, Dunietz, Gilman and Nir, Phys.Rev D41, 1522 (1990)


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Reconstruct exclusive B decays to CP eigenstates and flavor eigenstates and tag the flavor of the other B decay

Measure Dz between BCP and Btag to determine thesigned time difference Dt between the decays

( )

0 0

flav

0 *

Select candidates

( / , .)

and candidates

, .

CP

S

B

B J K etc

B

B D etc

y

p- +

Select events using, primarily,

leptons and 's from hadronic

decays & determine flavor

tagB

K B

B

i

i

i

Measure the and determine thedilut

mistag fractions ions

= 1- 2 w

wD

Determine the resolution function for Dz

( )2 23

1ˆ( ; ) ( ) / 2

2expi

i i

i

i

i

fR t a t

s p

=

== - -å

Overview of the analysis

z

0tagB

e-

( )4SU

K

0recB

0SK

J / y

e+

z

0tagB

e-

( )4SU

K

0recB

0SK

J / y

e+


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Canada [4/15]U of British ColumbiaMcGill UU de MontréalU of Victoria

China [1/5]Inst. of High Energy Physics, Beijing

France [5/51]LAPP, AnnecyLAL OrsayLPNHE des Universités Paris 6/7Ecole PolytechniqueCEA, DAPNIA, CE-Saclay

Germany [3/23]U RostockRuhr U BochumTechnische U Dresden

USA [36/253]California Institute of TechnologyUC, IrvineUC, Los AngelesUC, San DiegoUC, Santa BarbaraUC, Santa CruzU of CincinnatiU of ColoradoColorado StateElon CollegeFlorida A&MU of IowaIowa State ULBNLLLNLU of LouisvilleU of MarylandU of Massachusetts, AmherstMITU of MississippiMount Holyoke CollegeNorthern Kentucky UU of Notre DameOhio State UU of OregonU of PennsylvaniaPrairie View A&MPrincetonSLACU of South CarolinaStanford UU of Texas at AustinU of Texas at DallasVanderbiltU of WisconsinYale

10 Countries73 Institutions521 Physicists

The BABAR CollaborationItaly [12/89]INFN, BariINFN, FerraraLab. Nazionali di Frascati dell' INFNINFN, GenovaINFN, MilanoINFN, NapoliINFN, PadovaINFN, PaviaINF, PisaINFNN, Roma and U "La Sapienza"INFN, TorinoINFN, Trieste

The Netherlands [1/5]NIKHEF

Norway [1/2]U of Bergen

Russia [1/7]Budker Institute, Novosibirsk

United Kingdom [10/71]U of BirminghamU of BristolBrunel UniversityU of EdinburghU of LiverpoolImperial CollegeQueen Mary & Westfield CollegeRoyal Holloway, University of LondonU of ManchesterRutherford Appleton Laboratory


A snapshot

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Si Vertex-Tracker, Drift Chamber, DIRC (Cherenkov), CsI-Calorimeter, Superconducting Coil, Iron Yoke + RPCs/LSTs

The BABAR Detector

1m


19 19L. De Brunhoff

The PEP-II Asymmetric B Factory


Final collisions 12:43pm,Monday 7 Apr 2008

2020



The need for speed

2121


A tagged event0 0/ SB J Ky


2222



BABAR employed blind analysis and sophisticated maximum likelihood techniquesto extract maximum information from the data

in an unbiased manner

2323


sin2b in charmonium modes


2424


Measuring the Unitarity Triangle angles

0 0 0 0 *01

0 * * *

(*)0 0 0

*0

(*)0 0 0 0

0 , (2 ) , / , , , /

/ , , , with penguin :

sin 2

cos 2 , sin 2

( )

/

/

with angular analysis

( ) with Dali

S S L c S c S

S

S K J K K K J K b ccs

B J D D D D D D b ccd

D h D CP

B

B

J K

D h D K

J K

y y y

y

y

y

(*) (*) 0

0 0 0

(*) (*)

tz plot analysis

, ,

, with isospin analysis, with time-dependent Dalitz plot analysis

sin (

use . ., interference between and deca

2 )

ys

sin 2

B D D D K

B

B D K e g b cus b ucs


2525


sin2a and g


2626


Unitarity triangle constraints: sin2, sin2 measurements

The CKM matrix passesthe unique, new overconstrained tests


2727


The Unitarity Triangle deconstructed

CP-violating measurements

Tree-dominated measurements

Loop (mixing)-dominated measurements

All measurements except sin2bTree level

Loop dominated

Without sin2b

Mixing


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Not even wrong!

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It may not be quite so simple……


• There are discrepancies in CP asymmetries in bsss loop decays

_

• There are other hints that there could be additional phases, i.e., that there is more in the flavor sector than the three generation Standard Model

• Four generations can amplify the baryogenesis effect to the needed level: Hou (arXiv:0803.1234 [hep-ph] ) and can explain the various anomalies seen:Soni, Alok, Giri, Mohanta and Nandi (arXiv:0807.1971 [hep-ph] )

SuperB, with a 100x larger data sample,will resolve these issues, and allow us tounderstand the flavor sector of New Physics found at LHC


30 30L. De Brunhoff

The bottom line

BABAR has tested the Standard Model in unique ways by finding and then deeply exploring CP violation in the B meson system

BABAR has also done lots of physics beyond CP violation: Many other B decay studies, including other hadronic, leptonic and

semileptonic decays and rare loop-dominated processes Weak decays of charm, including long sought evidence for mixing t decays New hadronic states, some unexplained in QCD And just recently, the discovery of the hb, the ground state of the system

as of last week, 324 publications in refereed journals: PRL, PRD, NIM


0 0D D

bb

Documents

David Hitlin Caltech Let’s Celebrate Jonathan July 24, 2008