March 2000The First Data from BELLE1 First Data from BELLE HEP Seminar University of Chicago Daniel Marlow Princeton University March 13, 2000

March 2000 The First Data from BELLE 1

First Data from BELLE

HEP Seminar

University of Chicago

Daniel Marlow Princeton University

March 13, 2000


Physics MotivationDirect CP violation is perhaps the simplest case. Consider the CP mirror processes:

))(

))(

fBfB

fBfBACP

fBfB and

The CP asymmetry is defined as

The decay amplitudes are

and SWSW iiff

iiff eeAAeeAA

Note that the weak phase changes sign.


Direct CP Violation

Note that

Yielding

22

ffff AA

221121

SWSW iiii

f eeAeeAA

221121

SWSW iiii

f eeAeeAA

We need some sort of interference, two amplitudes, for example

)cos( 2 21

2

2

2

1 SWf AAAA

)cos( 2 21

2

2

2

1 SWf AAAA


Direct CP ViolationDespite its conceptual and experimental simplicity, there are two problems with direct CP violation:

•Cases where there are two comparable amplitudes that are large are (probably) rare.

•The strong phases are poorly understood, making it difficult to extract the weak (KM) phases that are of greatest interest.

This leads one in the direction of asymmetric B factories aimed at the study of indirect CP violation.


Indirect CP Violation

022

02

(0 sincos)( BeiBetB mimtmtimi

In this approach we provide the interference using state mixing, i.e.,

00BB


Indirect CP ViolationThus for a decay where is a CP eigenstate, we have two “indistinguishable” decay paths

fB 0

f0B0B f

Working through the algebra, yields a time-dependent CP asymmetry )(2sin)sin(2

)()(

)()()(

00

00

DMf

CP

tm

fBfB

fBfBtA

M DWhere and are the weak phases for the mixing and decay diagrams, respectively and

1

f

f ffCP


The Kobayashi-Maskawa Mixing Scheme

Where the second matrix is the Wolfenstein parameterization.

0* tbubtsustdud VVVVVV

Quark mixing is described via

The “d b” unitarity relation yields 3* AVV ubtd

1)1(

21

)(21

23

22

32

AiA

A

iA

VVV

VVV

VVV

M

tbtstd

cbcscd

ubusud


CP Phases in the Gold-Plated Mode

0DSKJB /0

)arg( tdM V

Decay

Mixing

The KM phase comes from the mixing.


The Unitarity Triangle

3A

Vtd

,

0,1

3A

Vub

3A

Vcb

1

2

3

The gold-plated mode determines the angle which is also called .

1


Existing Constraints

Existing measurements

of mixing and

limit the

allowed region in the

plane.

00BB

ubV

,

F. Parodi et al.


The Measurement

0B

0B

tag

CP

z

0DNeed to:

•Measure momenta

•ID leptons & K’s

•Measure vertices

e e

0K

/J


The Measurement

The time-dependent asymmetry appears mainly as a mean shift in the distribution between events tagged

as decays and

events tagged as

decays.

z

0B0B


The KEK-B Asymmetric Collider

KEK-B is similar to PEP-II in many ways, although there is a (potentially) important difference in the way in which the beams are brought into collision.

ee

ee


Beam Crossing Schemes

By colliding the beams at an angle, the KEK-B design achieves a simplified interaction region.

Moreover, every RF bucket (2 ns spacing) can be filled toachieve maximum luminosity. However, this approach risks destabilizing couplings between transverse and longitudinal modes of the machines.

A crab-crossing cavity is under development in case this proves to be a problem.


Linac Parameters

HER e- LER e+Parameter Design Achieved Design Achieved

Beam Energy 8 GeV 8.5 GeV 3.5 GeV 4.0 GeV

Charge/bunch 1.2 nC 1.2 nC .64 nC .60 nC

Transmission 100% 80-100% 100% 70%

Rep. Rate 50 Hz 50 Hz 50 Hz 50 Hz

Emittance <0.1 um .06 um <.25 um .4 um


IP @ / yx

HER e- LER e+

Parameter Design Achieved Design Achieved

Beam Current 1100 mA 600 mA 2600 mA 532 mA

Single BunchCurrent .22 mA 4 mA .52 mA 2.3 mA

Number ofBunches

5000 800 5000 1024

33/1 cm 100/1.1 cm 33/1 cm 100/1 cm

InjectionEfficiency

100% 80% 100% 80%

Ring Parameters


The Storage Rings

RF Cavity Stations


Recent Run Snapshot


The Magnet

March 2000 The First Data from BELLE 20About 10 Countries, 50 Institutes, & 200 People

The BELLE Collaboration


Key Belle Milestones• Early 1990’s - Japanese groups begin working.

• January 1994 - Collaboration forms.

• April 1995 - TDR Submitted.

…lots of work by lots of people in lots of places...

• Dec 18, 1998 - Belle detector completed (including SVD)

• Jan 26, 1999 - First cosmic ray with full detector.

• May 1, 1999 - Belle rolled into place.

• June 1, 1999 - First hadronic event!!!!!

• June 1999/July 1999 first serious running

•


June 1, 1999: Our First Hadronic Event


More Fun: SVD Included


First J/Candidate

• J/ee

– M(ee) = 3.1 GeV


Luminosity vs Time Profile

The KEK-B team has recovered at least part of the one-year schedule lag that they once had with respect to PEP-II.


The Silicon Vertex Detector


SVD Performance


SVD Performance

e

e

Bhabha miss distance


SVD Performance


SVD Tomography

X-Z distribution of primary vertices for all triggers, including beam gas.

The IP, the beam crossing angle, and various flanges etc in the IR are clearly evident.


CDC Performance


CDC Performance (Cosmic Rays)


Particle ID (dE/dx, ToF, & Aerogel)


Particle ID (dE/dx, ToF, & Aerogel)

0DD K


CsI EM Calorimeter Performance

MeV 50E

tionReconstruc 0

tionReconstruc


More CsI


Electron ID


K_L Muon Detector

The muon detectors, which are the largest, are made from standard soda-lime float glass (window glass).

An endcap module is installed.


Muon Detection

Note that there are no missing hits in the layers of the muon system, except at the locations.


0LK Detection

LKP

missP

hi

iS PPP,

4miss

First ~1000 hadronic events.


Energy Scan


Unstable Particles


Unstable Particles

Impossible without PID


A “Typical” Dimuon event

• J/

– M() = 3.1 GeV

–both muons tracks clearly evident in magnet return yoke

This event is consistent with

although there were no hits in the RPCs

LKJB /


Lepton-pair Spectra

ee


candidate KJB /


candidate KJB /


Charm Lifetimes


Charm Lifetimes


Lifetimes D

average) (world ps 015.1.057

ps 08.97.0


Lifetimes D

average) (world ps 015.1.057

ps 08.97.0


D Mass Plots0

w/o D cut* with D cut*


D Lifetimes0


Charmed Baryon

pKc Kpc

5.0px 5.0px


Combined Di-lepton Spectrum


Exclusive Mode Reconstruction

KJB /


Exclusive Mode Reconstruction

S

S

K

KJB /0


Neutral B Mixing


Conclusions & Outlook

• We have acquired about 600/pb of data, a tiny fraction of the 100/fb that is our Phase-I goal, but a good start nonetheless.

• The KEK-B accelerator is working with luminosity of almost

• The entire Belle detector, including the DAQ and offline reconstruction software, is working well.

• We continue in a constant struggle to increase the luminosity while fighting background.

-1-233 scm 10


Documents

March 2000The First Data from BELLE1 First Data from BELLE HEP Seminar University of Chicago Daniel Marlow Princeton University March 13, 2000