Flavour Physics at t -c Factories

Frascati Jan 19th, 2006 SB - Flavour physics at tau-charm Factories 1

Stefano BiancoLaboratori Nazionali di Frascati dell’INFN

Frascati, January 19th, 2006

Flavour Physics at-c Factories


CONTENTS

1. Past , Present and Foreseeable Future for TauC factories2. Flavour (Charm) Physics(see Antonio’s talk for onium)3. A List Of Open Questions and A Few Answers


1.

Past , Present and Foreseeable Future for TauC factories


Charm discoveryK.Niu, E. Mikumo, Y. Maeda Prog. Theor. Phys. 46 (1971) 1644

D+ K+

First observation of D mesons at accelerators

I.Peruzzi et al., Phys. Rev. Lett. 37(1976) 569.


Charm quark detectors over the years

R704E760E835

NA14

ARGUS

MARK IIII

E691CLEO2CLEO-C

PANDA

NOW

BABAR,BELLE

CDF,D0

BES

NA1BNL

SPEARADONE

COMPASS


• √s =3.770GeV ’’ coherent production of D meson pair

ee(3770)DD WHY ?

• Large , low multiplicity • Pure initial state: no fragmentation• Double tag measurements: no background• Clean neutrino reconstruction• Coherent initial state

CLEO-c


Tau-charm Factories proposed in the past

• 1987 proposed at CERN• 1989 proposed at SLAC• 1990 proposed in Spain• 1992 proposed in ITEP • 1994 proposed at Argonne• 1996 micro-workshop at Frascati (G.Capon

Convener)• …• 2005 a study in Frascati


THE CHARMING COMPETITION• CLEO-c tau-charm factory, running. goal=3fb-1 DD

– started Sep 2003, as of April 2005 265 pb-1 integrated at ’’. Luminosity below project goal=3 1032cm-2s-1. End in 2008.

• Beijing tau-charm factory BEPC-II, design 1033cm-2s-1, commissioning in 2006

• BABAR (end in 2008)• BELLESBELLE ???• Frascati tau-charm Study (2005):

– 2x108 reconstructed DD events– L=1034cm-2s-1– 100fb-1/y– start in 2011– 30x CLEO-c– 2x BEPC-II after 1 y– ~10x BABAR/SBELLE withmuch better systematics


Detector(CLEOIII –like)VERYCHALLENGINGAND AMBITIOUS

• tracker• RICH• ECAL• solenoid• ermetic 4

geometry• potent DAQ• open trigger

1.5 T now,... 1.0T later

93% of 4p/p = 0.35%

@1GeVdE/dx: 5.7%

@minI

93% of 4E/E = 2% @1GeV

= 4% @100MeV

83% of 4% Kaon ID with

0.2% fake @0.9GeV

85% of 4For p>1 GeV

Trigger: Tracks & ShowersPipelinedLatency = 2.5s

Data Acquisition:Event size = 25kBThruput < 6MB/s


2. Flavour Physics

at a tau-C Factory

(see Antonio’s talk for onium)


High-impact Physics & Engineering Database

bt

sdu c

CPV, mixing and rare decays in

Charm sector are a probe for New Physics

Why (only) 3 families ?

Quark c is the only HQup-type probe

In the charm sector, SM contributions to CPV, mixing

and rare decays are small (GIM)

But how small?CPV asimm 10-3

D0D0bar mixing 10-3—10-10Rare decays 10-9 – 10-19

Higgs ?

HI ENERGY

SM

FSI corrections are important

Quantitative predictions via 1/mQ expansions are possible

Quark c is the lightest heavy quark

Studying the c-quark provides sensitivity and discovery potential for New Physics. After the

discovery (?) of Higgs @ LHC, New Physics manifestationsin c-quark (and in b-quark) important to

distinguish among models.

FSI corrections are important

QCD LO ENERGY


• √s =3.770GeV ’’ coherent production of D meson pairs• L~1034cm-2s-1, 100 fb-1/y• 2x108 DD pairs detected (30% eff*acc, extrap. from CLEO-c) , in uniquely

clean environment, per year.• Search for New Physics:

1. Direct CP Violation in SCSD asymmetries, and directly in integrated rates. Sensitivity 10-4, SM PREDICTION 10-3.

2. Search for direct CPV in CFD and/or DCSD, where SM PREDICTS NO CPV3. Mixing exploiting coherence, unique feature of threshold production.

Cannot study mixing in time evolution of rates, but only in integrated rates. In most channels, DCSD concurrent process does not exist thanks to Bose-Einstein statistics (coherent C=-1 quantum state). By comparing semilept and hadronic, measure strong phaseshift

4. Rare decays: FCNC D+ h l+l-, D0l+l-, SM PREDICTION 10-9 Sensitivity 10Sensitivity 10-7-7 - 10 - 10-8-8

ee(3770)DD “NEW PHYSICS” PROGRAMME

Bibliography:1. SB, Fabbri, Benson, Bigi Riv.Nuovo Cim. 26,7-8, 2003 hep-ex/0309021. 2. I.Bigi and A.Sanda CP Violation, Cambridge, 2000.3. CLEO-c proposal (2001).4. Burdman Shipsey Annu. Rev. Nucl. Part. Sci. 2003. 53:431–995. Frascati Futuro report (Antonelli, SB, Bloise, Bossi, Miscetti et al.)


Also, tau physicsee’’

• √s =3.770GeV ’’ production of tau lepton pairs, ~3nb.• L~1034cm-2s-1, 100 fb-1/y• LNV decay sensitive to SUSY, (109 events) / (three

years). BABAR best limit 7x10-8 (90%cl) dominated by systematics, background Running at threshold reduces systematics.

• Robust Standard Model physics programme:– precise measurement of mass– weak couplings (purely leptonic and semileptonic decays)– test of CVC rule, and implications on anom. magn. moment of

muon.– etc (see Gino Isidori’s talk April 2005 Frascati, and Futuro

report Sect.5.5)


CPV ASYMMETRIES


For a two-amplitude decay

ii = strong phase

CP asymmetry:

2 different weak amplitudes strong phase-shift

AAtottot = g1M1ei1 + g2M2ei2

CP conjugate

AAtottot = g1M1ei1 + g2M2ei2

** **

aaCPCP==2Im(2Im(gg2 2 gg11**) sin() sin(11--

22)M)M11MM22|g|g11||22MM1122+|g+|g22||22MM22

22+2Re(+2Re(gg2 2 gg11**)cos()cos(11--22)M)M11MM22

|Atot|2-|Atot|2

|Atot|2+|Atot|2==

CP VIOLATING INTEGRATED ASYMMETRIES

are needed for CPV asymmetry Single Cabibbo-suppressed decaysIn DSCD and CFD only one weak amplitude NO CPV WITHIN SM


In plain words…

• SM predicts CPV at the 10-3 level in SCSD observation would be a *** result

• SM predicts ZERO CPV in CFD and DCSD observation of CPV in those decays is a ***** discovery of New Physics


Search for CP violation via Dalitz plot analysis of Singly-Cabibbo-suppressed Decays

• Use full decay info, not only BR must determine amplitude coefficients and phases

• Final state results from the interference of all intermediate states

• Differences between amplitude and/or phases patterns in a Dalitz analysis betw conjugate states (i.e., D+ vs D-), would be evidence of CP violation (ref. I.Bigi,A.Sanda “CP Violation”)


Ds , D+ KK

Ds+ K+ K+ D+ K+ K+

D sD

2Km

2KKm 2

KKm

2Km

KKm


+ -2K K

m

- +2K π

m

K+ Kprojection

K projection

Yield D± = 7106 92

S/N D± = 8.62

Decay Fraction and phases K*(892) = 20.7 1.0 % (0 fixed)(1020) = 27.8 0.7 % (243.1 5.2)°K*(1410) = 10.7 1.9 % (-47.4 4.9)°K*

(1430) = 66.5 6.0 % (61.8 3.8)°f0(1370) = 7.0 1.1 % (60.0 5.3) °a0(980) = 27.0 4.8 % (145.6 4.3)°f2(1270) = 0.8 0.2 % (11.6 7.0) °(1680) = 1.6 0.4 % (-74.3 7.5) °

Preliminary

D± KK


Coefficients: D±,, DD++,, DD--

Phases: DD±±,, DD++,, DD--

D+/D- split sample analysis Preliminary!

No evidence of CPV


D0D0 MIXING


0

0

2221

120

011

PP

HHHH

PP

ti

2/jkjkjk imH

Processes which allow mixing appear in H12 and H21.

00 PP

The time evolution of flavour eigenstates is given by the Schrödinger equation

00 , PP

If are not mass eigenstates. Mass eigenstates are(assuming CP conservation)

002,1 2/1 PPP

012 H 021 H 00 , PP,

)cos(21)( 2

200 1 mteeetPP

ttt

and mixing amplitude is

mx

2y

Mass and width differences are parametrizedby

Formalism of P0-P0 mixing 1x 1y

mixing can be described by the ratio r

2)()( 22

0

00 yxfP

fPPr

|x|>0 mixing is caused by

genuine

transitions(f=2)

x splits masses

|y|>0 mixing is caused by the

short-lived component

disappearing rapidly, leaving behind the long-

lived component,

made of and

y splits lifetimes

0P 0P

00 PP


2

,,2

222

bcsW

dq

mmmm

SHORT DISTANCE

KK,

0D0K

0D0K

LONG DISTANCE

q SD/LD x=m/ y=) c SD~LD 0.48 100% s SD<<LD <5% <1% t SD>>LD 0.75 ? t SD>>LD >22 ?

)(0 sdK

)(0 bdBd

)(0 ucD

)(0 bsBs

K0, D0, B0 _ Where’s The Difference ?


Theoretical “guidance”From compilation of H.N.Nelson

hep-ex/9908021

Triangles are SM x Squares are SM

y

Circles are NSM x

“D0D0 mixing is a window on New

Physics”

_

310, SM

yx


2

_

Measure yCP, the y parameter for CP

eigenstates

Measure r

2)()( 22

0

00 yxfD

fDDr

mixedKCP

KKCP

KKKKCP

SS

HADRONIC DECAYS

SEMILEPTONIC DECAYS

Kf Kf

(1 +2)/2

TECHNIQUES FOR STUDYING D0D0 MIXING (I)


_

Measure r 2)(

)( 22

0

00 yxfD

fDDr

HADRONIC DECAYS

Kf

0* DD

D* tags D0

flavour

KDD 00

mixingCabibbo-

Favoured Decay

trytrrefDfDr DCSDCS

tWS 2)(

)( 2

0

0

KD0

Double Cabibbo-Suppressed Decay

Strong phase between CFD and

DCSD mixes x and y

sincossincos

yxxxyy

0D Kuss

uc s

du

c

csV

udV

cu u

d

us

KcdV

usV

0D

via

TECHNIQUES FOR STUDYING D0D0 MIXING (II)


_

Measure r 2)(

)( 22

0

00 yxfD

fDDr

0* DD

D* tags D0

flavour

mixingCabibbo-

Favoured Decay

SEMILEPTONIC DECAYS

Kf

KDD 00

0DKu

ss

uc s

c

csV

rfDfDrWS

)()(

0

0

via

TECHNIQUES FOR STUDYING D0D0 MIXING (III)


• Direct measurement of yCP requires good lifetime resolution • Measuring rws in hadronic decays requires to disuntangle rDCS from r; and the knowledge of

• Measuring rws in semileptonic decays provides the r parameter, but it is experimentally more difficult•MEASURING rws at tau-C PROVIDES THE r PARAMETER, SINCE QUANTUM CORRELATIONS FORBID DECAY TO IDENTICAL FINAL STATES (NO DCSD POLLUTION).

TECHNIQUES FOR STUDYING D0D0 MIXING (Concl.)

_


STATUS OFD0D0

MIXINGAS OF SPRING 2004


• √s =3.770GeV ’’ coherent production of D meson pairs, L~1034cm-2s-1, 100 fb-1/y• 2x108 DD pairs detected (30% eff*acc, extrap. from CLEO-c) , in uniquely clean

environment, per year.• Standard Model physics programme: Absolute branching ratios; Vcd, Vcs from

semileptonic decays; SL Form Factors; Charm decay constants fD from Dlight quarks in Dalitz plots; etc.

ee(3770)DDSTANDARD MODEL FLAVOUR PHYSICS

Ref: SB, Fabbri, Benson, Bigi Riv.Nuovo Cim. 26,7-8, 2003 hep-ex/0309021. I.Bigi and A.Sanda CP Violation, Cambridge, 2000.


• Charmonium spectroscopy• QCD• Hybrids, glueballs

eeJ/X


QUESTIONS, AND MY VERY FEW ANSWERS

• Physics– Is the cF a significant help to disentangle among non-SM models after the discovery of

SUSY ?– Are the SM measurements significant in the field of b and c physics ?– Is the SM programme of a cF strong enough to allow success even is SUSY is not

discovered at LHC ?• Detector

– must be all-purpose detector !– Can we start design ?– Impact on Frascati infrastructure ? VERY BIG, INTERNATIONAL ENTERPRISE– Cost ?

• Machine– Impact on Frascati infrastructure ? VERY BIG, INTERNATIONAL ENTERPRISE– symmetric/asymmetric ?– Fits DAFNE building ? NO– Cost 100MEuro ? MORE

• Competition– Is a 2011 Frascati tcF going to be competitive and timely wrt CLEO-c and BES ?– Is a tcF really necessary after BABAR and, expecially, BELLE/SBELLE ?

• Sociology– Is the Frascati community interested in working hard on a onsite world-class project ? YES !– Is the whole INFN community interested ?– Is the world community interested ?– This is a Big Science project, Isn’t Big Science HEP over ?


http://www.lnf.infn.it/c

onference/dif06/


CONCLUSIONS

• The Physics programme at a tau-C factory is very large and robust:

1. BSM: CPV, Mixing, Rare decays, tau rare decays2. SM: absolute branching ratios, meson decay constants, CKM elements from semileptonic decays, charmonium spectroscopywith some items unique or superior wrt B-factories (underlined above). Is this uniqueness sufficient to justify it ?

• Machine and detector are likely to be costly and challenging, expertise does exist in Frascati but has to be an international enterprise.

• Timing is the critical issue against competition

•Flavour physics is necessary in the LHC era if “Beyond the SM Physics” is discovered


QUESTIONS SLIDES

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Flavour Physics at t -c Factories