over 1 million reconstructed!!

3/23/99 FOCUS first results <Jim Wiss> 1

Over 1 million reconstructed!!

Successor to E687. Designed to study charm particles produced by ~200 GeV photons using a fixed target spectrometer with upgraded Vertexing, Cerenkov, E+M Calorimetry, and Muon id capabilities. Includes groups from USA, Italy, Brazil, Mexico, Korea

1 million charm particles reconstructed into DK , K2 , K3

2

Preliminary measurement of the Ds+ lifetime

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1.7 1.75 1.8 1.85 1.9 1.95 2 2.05 2.1

Signal Region

Sideband Region

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-1 -0.8 -0.6 -0.4 -0.2 0 0.2 0.4 0.6 0.8 10

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-1 -0.8 -0.6 -0.4 -0.2 0 0.2 0.4 0.6 0.8 1

Signal Region

Sideband Region

Accepted Region

(Ds+) = 0.506

0.008 sys (ps)

Using E791 (Ds+) = 0.518 0.014 0.007 ps

We project:WA is (Ds+) / (Do) = 1.214

0.017 See talk of Harry Cheung

We use 5668

Ds+ decays in

~50% of FOCUS to suppresses long-lived backgnd from D+K- + +K+

Also allows us to enhance S/N with

cos cut

cos K

Theory (Ds+) / (Do) =1.07 1.20

Ds+ Do

Ds+ and Do have unique CF non-spectator decays

WA WX


PRELIMINARY D*D Mass Splittings

We are seeing very strong D*o Do signals in FOCUS with our new & improved E&M calorimeters. Project a final sample of 25000 D*o Do decays .

CLEO92 has provided the best past data on D0* mass, widths, and branching ratios from ~1200 D*o Do decays

~50% FOCUS

D*o - DoD*+ - D+

IE-IE 0’s only


PRELIMINARY Mass splittings

PDG98

PDG98

Isosplittings depend on same physics as the D decay constant

HQ98 LGT•Both °samples consistent with PDG98 already w/ smaller errors !

S/N

24% of FOCUS


We are even getting our first glimpse at Ds*+

Preliminary

~20% FOCUS IE only

Ds*+ Ds+


“Golden” signals with pi0’s

K K K2 K2

K3

Y=3545Y=12713Y=996

Y=1396

K3Y=303

Y=2150

Signals based on 20% of FOCUS No optimization of cuts!

# per 5 MeV

•Can study a rich new set of charm decay

•Many are required to complete isospin amplitude triangles


Beyond the D*

HQET predicts a rich L=1 spectrum

• 2 broad states with s-wave decays (CLEO has evidence for 1)

•2 narrow states with d-wave decays (seen in e+ e- & N)

•Predictions are made for masses, widths, and angular distributions and the relationship to B** splitting.

FOCUS has PRELIMINARY signals for

D01D* D0*

2D*

D0*2D D+*2D

D*s?K DThe low multiplicity of primary vertex gives photoproduction an advantage for D** study.


PRELIMINARY D** signals ~27% FOCUS

WS

WSWS

D2*0 (2460)

D2*+ (2460)

D1(2420) D2*0(2460)

Do1 , D*o

2 D*-+(D)+

reflection

unresolved in E687 except by angular cuts

Ds+*D0K

DsJ(2573)+?

Ds** (D)K+

D1(2420) absent by parity

We observe

•2 peaks in D*+-

•1 real peak in D+-

•1 real peak in D0+

•1? peak in D0K+

Also see reflections at M-m from D*°D with missing °

Angular distributions can often be used to disentangle states and confirm HQET predictions.


Dalitz Amplitude Analyses•Dalitz analyses are a traditional strength of E687 which has published on:

• K- + + K- +o Ks- + K-K+- ++-

•Dalitz analysis provides powerful probes on charm hadronic decay

•Underscores the importance of quasi-two body decay and extends tests of factorization models to vector-pseudoscalar decay

•Often highly unusual resonances dominate charm Dalitz plots.

•Allows one to directly investigate non-spectator effects such as W-annihilation

•Provides new handles on charm CP violation by comparing the phases and amplitudes that one gets for particles versus antiparticle decay. Best in Cabibbo suppressed decays.

•Provides a preview of the FSI complication for beauty

• Studies on many Dalitz plots studied by E687 are already underway. I will discuss two interesting Dalitz plots featuring decays with an unusual number of final state kaons.


Favored D decays with “unusual “ numbers of kaons

Conventional spectator but with weird resonances?

NR Weak Annihilation ?

Resonant Weak Annihilation?

Too few kaons!

An example is Ds

BR is large ~1.4% suggesting a Cabibbo favored decay

Cabibbo favored would produce a s s u d as final quarks and no kaons appear in the final state. How are they lost?


Preliminary FOCUS Ds Dalitz plots (~40%)

Observe:

•f0(980)

•f2(1270)

•f0 (1500)

Clearer in FOCUS

No evidence for WA

(770)

•NR

f2f2

•Dominated by weird resonances with simultaneous KK and couplings•No evidence for non-spectator decays such as NR or


a0(980) f0(980)

PRELIMINARY D0Ks K+ K- Dalitz plot

a0(980)?

f0(980)?

2 spectator diagrams with resonances which couple to ’s and K’s

Y=395S/N=17

~50% FOCUS

We use D* tagging to determine strangeness of K°s

Too many kaons

Here we have only an s u d quarks in the final state yet three kaons appear!

m²K+K-

m²K+Ko


Studies of Cabibbo Suppressed decays

•FOCUS’s powerful Cerenkov ID and very large data sample gives it unique opportunities to study Cabibbo Suppressed Decays

•Will present evidence for five DCS Decays ( 2.50.5 decays are new!)

See talk of Jon Link

•Historically the pattern of Cabibbo suppression has been full of surprises and has yielded unique insight into hadronic decay mechanisms to challenge models

•The rate for DCSD is often very different than tan4C

•D° DCSD interferes with hadronic decay mixing. This is good news / bad news since small amplitudes are best measured through interference

•Differences in DCSD/CF Dalitz plots can probe Do mixing (T. Liu)

3/23/99 14

DCSD : D+ K+ +-

~40% of FOCUS Data

Y(D+)=17228Y(Ds

+)=22421

(K+ +-)/ (K- + +) = (0.650.11)%

3 tan4Cabbibo (+/0) tan4C

CL1<0.1 CL1<110-8

Preliminary FOCUS

5913 E791

K+ +-)/K- + + = (0.68 0.15)% PDG98

Our results already much better than PDG98 ( 3 E791)

M(K+ +-)


PRELIMINARY (~40%) D° DCSD

rs

ws

WS mass & fixed by RS

Here we look for WS D° decays where the kaon has the same sign as the D+* decay pion. This is also a classic way to search for mixing and could interfere with mixing. BR(DCSD) WS/RS

Y=7221.6±87.80

M=0.1455

W=0.91

Y=60.337±21.40

rmix

K++

D0 D0

-

K++

D0

-

D*+

D*+

DCSD

mixed CF


Relative WS/RS ratio versus CITADL Cuts

W -WK

Slight variation in BR as pid cuts are tightened. Would expect exponential decrease if double mis-id. The signal level is consistent with existing world’s average but higher than CLEO’s recent measurement at APS

Cut variations on 19/155 with K candidates.

K PDG

PDGerror

W -WK

ws/rs Miss-id yield

MC study


PRELIMINARY D +sK+K+-

~50% PRELIMINARY

This is the first observation of D+

s DCSD

The rate relative to K-K++ is 1.5% (~6 tan4Cabbibo)


PRELIMINARY D+ K+K-K+~40% FOCUS

Y(D+ ) = 27±7 Y(Ds

+ ) = 28±7•Ds

+K+K-K+is a SCSD

•D+ K+K-K+ is a C = -S DCSD which cannot occur via a spectator diagram.

(D + K+K-K+)/ ( D +) = (1.450.39)10-4

Just below PDG 98 limit from E687 of Br < 1.410-4 CL=90%

Our rarest DCSD BR yet : (D + K+K-K+) / (K-++) tan4C/2

No evidence for D+ K

A KKK Dalitz analysis may shed light on the KKK decay mechanism.


Rounding out the all kaon final states...

KsK D + KsKsK+

45% Focus

Y=208

Altogether we show SIX all kaon charm decays

D0 K+K- D + KsK Ds+ KsK

D0 Ks K+ K- D + KsKsK+ D+ K+K-K+

These two are difficult for us to study because charm in FOCUS is brought out through vertexing and the Ks in FOCUS generally verticize downstream of the SSD.

Y=491 Y=556

50% Focus


c & *c Spectroscopy

80% FOCUS

cpK

c specta

*c spectaWe can study all of this spectroscopy!


Preliminary c - c mass differences

M= 167.450.170.36 MeV

See talk of Eric Vaandering

Theoretically one expects

M(c0) > M(c

++)

But world’s data including our measurement has M(c

0) < M(c++)

by about 1.5

M= 0.280.310.15 MeV

M=167.170.260.27 MeV

c++ - c

+

c0 - c

+

c++ - c

0


Kinky decays of the c+

c+- K++

~75% FOCUS

Y=607 in ~22% FOCUS

Y=253 in ~22% FOCUS

CLEO saw 487 events

E687 saw 56 events

•We have unique abilities to reconstruct the - n -

•Will study (1385) since only contributions are internal W and WX

23

A Gallery of +c decays

- + + K-++ +K-+

pK-+

SCSD

1st reported by Selex HQ98

~70% Focus

~20% Focus

~30% Focus

~75% Focus

Using the 3 favored decay modes, we

project a sample of 860 +c decays

~30 times the E687 lifetime sample

which provides the best c lifetimes


Search for CP violating SCSD decaysE791

FOCUS (26%)

DKWe normalize to DK-+ to eliminate 4% production asymmetry.

World’s best data using 26% of Focus!

Look for (DK+K-) (DK+K-)

Tag D charm through D* D

Much less DKReflection


Semileptonic Mixing Searches

WS

rmix

K+

-

+

D0 D0

K-

+

+ RS

D0

D*+

D*+

from another event tmix

WSt

RS etr

tIetI 22

2)()(

Limit follows from fitting time evolution of WS and RS signal. No DCSD interference.


Mixing sensitivity

•FOCUS projected sensitivity is rmix ~ 0.15%

•Including electrons we project rmix ~ 0.1%

•Present E791 limit rmix < 0.50% (90% CL)

We have unique advantages in searching for direct differences between CP-even eigenstates such as D°K+ K- and states of mixed CP such as D° K- + or CP odd states such as Ks or Ks

We expect a yield of from 5000-10000 D°K+ K- decays. This should give us a lifetime measurement for CP even states of better than

()/ < 1.5%

3/23/99 27

FOCUS Semileptonic Physics•We improved all aspects of our lepton id system including an entirely rebuilt inner muon system, a new outer muon system, a rebuilt inner E&M calorimeter and an enhanced outer E&M calorimeter.

RS-WS = 64244

M(K)

K*l from 80% Focus •We project a ~50 fold increase over E687 which published form factors for each of these states

Our projected Kl yield should make us very competitive with other charm experiments!

Our vertex tagging gives us the ability to study Kl without D* tagging Enormous yield

3/23/99 28

Soft pion tagging as means to absolute BF

D*+

K+

~

D0

D_(recoil)

_

Pt2

r.s w.s.

GeV2Pt2 = x2 + y

2 , i = 13.8 Pi

+ Pi.r

Can tag the presence of a D° by observing a right sign which balances Pt with a reconstructed D . You then count the number of D° decays into a particular final state, correct by efficiency and ratio to find an absolute branching fraction. Low primary vertex multiplicity is a big advantage.

Proof of Principle 1: Is there an excess of RS over WS events at low Pt ?

30% FOCUS

Proof 2: Can we reconstruct both D’s in an event?

Already have a copious sample of very clean events with both reconstructed D’s Expect 7500


What I left out•Production dynamics => Unique tests of QCD

•Xf , PT and E dependence compared to NLO -g fusion

•Charm/Anticharm asymmetry as probes of fragmentation

•Kinematic correlations in D D events as probes of NLO QCD

•Amplitude analyses for 4 body and 5 body final states

•Semileptonic decays

•Semileptonic Form factor measurement.

•Cabibbo suppressed semileptonic decay

•Rare or forbidden decays

•Many of these studies are already underway or will start shortly!

over 1 million reconstructed!!

Documents

strong d

results preliminary

dwave decays

d mass splittingswe

d reflection unresolved

ds focus

ds decays

ds lifetimeusing e791