08/09/2007 Tania Moulik, B Spectroscopy at Tevatron, ISMD 2007 1 International Symposium of...

08/09/2007 Tania Moulik, B Spectroscopy at Tevatron, ISMD 2007 1

International Symposium of Multiparticle International Symposium of Multiparticle Dynamics 2007Dynamics 2007

09 Aug 2007

Tania Moulik (University of Kansas)On behalf of CDF & DØ

collaboration


Protons :LINAC Booster Main Injector Tevatron 400 MeV 8 GeV 150 GeV ~1.00 TeV

Antiprotons :120 GeV protons (MI) Ni Target antiprotons debuncher+accumulator+recycler Tevatron

6 Km

3 Km

150 m

TeVppEEmms 96.1))cos((2 212122

21

Accelerator chain Accelerator chain Accelerator chain Accelerator chain


Overview of DetectorsOverview of DetectorsOverview of DetectorsOverview of Detectors


QCD simplifies in the limit of one heavy quark mass Heavy Quark effective field theory (HQET). Mass scale for heavy baryons different from quark confinement scale ~ 400 MeV governing physics of light hadrons. mt, mb, mc >> QCD >> ms, mu, md

Heavy baryons good way to study non-perturbative QCD (Quark interactions inside hadrons described by non-perturbative QCD)HQET successful in describing Qq systems. Continue to test it for Qqq systems. Features of HQET: Treat heavy quark as static source of color field. In case of baryons, view Light quarks forming a diquark pair and independent

of the heavy quark in the limit of infinite heavy quark mass and it looks the same for any flavor or spin orientation of the heavy quark

Also test Heavy baryon predictions from other theoretical models (approximations to QCD): 1/Nc expansion, sum rules, lattice QCD

B spectroscopy Motivation B spectroscopy Motivation B spectroscopy Motivation B spectroscopy Motivation


Experimental timeline of heavy B baryonsExperimental timeline of heavy B baryonsExperimental timeline of heavy B baryonsExperimental timeline of heavy B baryons

For a long time only known heavy B baryon was b. Semileptonic decays observed at LEP between 1992-1998 and also at

Tevatron. Hadronic decay modes (Fully reconstructed == Measure mass precisely)

(J/ ) (1991)@UA1 (1997)@CDF c (2006) @ CDF and continued to be studied at

Tevatron.

Recent discoveries at Tevatron of b and b, and the excited B states lead to an exciting new era of testing theories describing quark systems with a heavy baryon. Potential to discover other new B baryons, …and so on…b


The quest for b BaryonsThe quest for b BaryonsThe quest for b BaryonsThe quest for b Baryons

Light diquark system : spin 0 () (I=0, Jp=0-) / spin 1 () (I=1, Jp=1+) state

state (0+) heavy Quark (1/2+), state (1+) heavy Quark (1/2+)

)23(* Pb J

Host of hadron discoveries led Enrico Fermi to exclaim "Had I foreseen that, I would have gone into botany"

)21( Pb J

http://en.wikipedia.org/wiki/Enrico_Fermi

http://en.wikipedia.org/wiki/Enrico_Fermi


Mass predictions and hierarchiesMass predictions and hierarchiesMass predictions and hierarchiesMass predictions and hierarchiesWhy are and masses different?

uus – (uds) mass difference believed to be due to difference between u-d and u-s hyperfine interactions :

And other predictions :

hypIE

i ji

ji

ii v

mmmM

Hyperfine splittings

Zeldovich, Sakharov, Sov. J. Nucl. Phys. 4(1967) 283

51.2

*

*

KK

BB

MMMM

MMMM

MM

MMbb

MeVMMbb

194

MeV

MeV

MeV

1.117.6068)(

0.92.5824)(

1.87.5805)(

b

b

b

M

M

M Predicted mass hierarchy:

M(Λb)< M(b) < M(b)

Karliner, Lipkin, hep-ph/0307243, Phys. Lett. B 575, 249(2003)


Observation of Observation of bbObservation of Observation of bb

Inb light quarks in symmetric state

Together with heavy quark leads to doublet of baryons

Ground state decays strongly to-type baryons (antisymmetric configuration of quarks) emitting pions. Look for b in decay mode b . Number of theoretical predictions:

)(),(,1,1 ddbuubJI bbPl

)(2

3)(

2

1 *b

Pb

P JandJ

180 – 210 MeV

10-40 MeV (Mass splitting)

5-7 MeV

0.400.07 MeV (Isospin splitting)

)()( 0bb mm

)()( *bb mm

)()( bb mm

)()()()( ** bbbb mmmm


b b bb , , bb cc , , cc p p

K K b b bb , , bb cc , , cc p p

K K Start with constructing b Then, Search for narrow

resonances in the mass difference distribution

Backgrounds: tracks from b fragmentation

(e.g. hadronization of the b quark) and underlying event.

Physics background, B0 D-+; D- -K+- Also B0’s from B**

decays.

Optimize cuts with b signal region blinded.

b cPDG = 422 m, Cut requirement:

c (b) > 250 m

5.565 < m(b) < 5.670 GeV

mmmQ bb )()( 00


bb Results Resultsbb Results Results

Fit to breit-wigner convoluted with double gaussian. Width of breit-wigner :

No isospin splitting sensitivity

Measure average

22

6

1

pfM

Mp

q

q

qq

)()()()( ** bbbb mmmm

)()( *bb mm

)( bm

)()( *bb mm .)(.)(2.21 4.0

3.00.29.1 syststat

.)(7.1.)(8.5807 0.29.1 syststat

)( bm .)(7.1.)(0.12.5815 syststat

)( *bm

)( *bm

.)(7.1.)(0.5829 6.18.1 syststat

.)(7.1.)(0.20.5836 syststat


Observation of Observation of b b (dsb)(dsb)Observation of Observation of b b (dsb)(dsb)

Vertex Prob 2 > 1 %pT () > 1.5 GeV2.80 GeV < M () < 3.35 GeVpT (J/) > 5 GeV

Vertex Prob 2 > 1 %Track with higher mom.

Assumed pion1.05 GeV < M (p) < 1.125 GeV

At most 2 hits in tracker before p vertex.

Imp. Param sig. > 3(both tracks)At least > 4 (for one track)

Imp. Param sig. > 3(pion track)Decay length () > 4 * uncertaintyDecay length () > 4 * uncertainty

pJb ,,


Special techniques..Special techniques..Special techniques..Special techniques..

p

For particles like the b-, usual impact parameter cut

requirement for track reconstruction could result in missing the and proton tracks from the and - decays.

At DØ entire J/ dataset was processed with “special” extended tracking:

• Impact parameter cut from 2.5 cm 10.0 cm

• Maximum acceptance angle 0.08 rad 0.2 rad

•At CDF candidate tracks are refitted, with Si hit requirements.

→p- --


bb Results Results bb Results Results

Likelihood Fit Results : M (DØ) = 5774 11 (stat.) 15 (syst.) MeV -- [1]

M (CDF)= 5792.9 2.4 (stat.) 1.7 (syst.) GeV ) – [2] (Theory : 5.793 - 5.814)

Likelihood Fit Results : M (DØ) = 5774 11 (stat.) 15 (syst.) MeV -- [1]

M (CDF)= 5792.9 2.4 (stat.) 1.7 (syst.) GeV ) – [2] (Theory : 5.793 - 5.814)

15.2 4.4

17.5 4.3

[1] PRL 99, 1052001 (2007)[2] arXiv:0707.0589


Observation BObservation B11 and B and B22**Observation BObservation B11 and B and B22**

Among B mesons, Only ground 0- states

B+,B0,Bs,Bc and excited 1- state B*

considered established.Quark models predict 2 broad and 2 narrow P-states:

Broad states difficult to distinguish Width ~ 100 MeV (Decay through an S wave).

Narrow states easier to identify Width ~ 10 MeV

(Decay through D wave)

)1(),0( *1

*0

PP JBJB

)2(),1( *21

PP JBJB

2

12

1

LJ

JJ

l

l

M..Di Pierro and E. Eichten, Phys. Rev. D 64 (2001)



Look for mesons in decay modesReconstruct

BB

BBBB

BBBB

*2

***2

**1

;

; KJB

.)(29320915

36.5)(19.5

stat

GeVBM

Look for track from primary vertex. Combine with B+Plot

)()( BMBMM

),,()1(),,().1(),,(.)(

)()()(

2322221111

MDfMDffMDfNMF

MFMFMF

sig

bkgsig

),()( 0)2(

5

0

00 kkF

k

k

x

xx

Breit-wigner convoluted with gaussian. Resolution in M determined fromsimulation

MeV35.078.45

PDG, J. Phys. G 33 1 (2006)

)(

)(),(

32

*23

*11

E

BBMBBM



D0 CDF

M(B1) (MeV) 5720.62.4 1.4

M(B2*) (MeV) 5746.82.4 1.7

Unable to resolve the B2* decaying through B* and emission of and through B.

Masses agree to within 1

8.01.1

6.11.2 .)(3.5725

stat

5.06.0

7.18.1 .)(9.5739

stat


Observation of BObservation of Bss**Observation of BObservation of Bss**

Analysis similar to previous modeLook for the decay

KBBs*2

B*s2B+K-

Where is B*s2B* K ? should be

here MeVKMBMBM s 20)()()( **2

Claim : Suppressed due to L=2 orbital angular momentum and small mass difference

D0 does not observe the Bs1 peak. Would be interesting to look at more data.


BBss* Interpretation and Theory* Interpretation and TheoryBBss* Interpretation and Theory* Interpretation and Theory

Theory predicts equal branching ratios of Bs2* B*+K- and B+K-. Experimentally should be observed as resonance displaced to lower M by photon energy 45.78+-0.35 MeV.Rate supressed by a factor (No signal expected with current statistics)

What about Bs1 B*K+? In (bd) system, M(B2*) – M(B1) = 26.2+-3.1+-0.9, ..Applying to Bs

system… Expect Bs1 = 5813 MeV i.e. < M(B*)+M(K-) (5819 MeV)…In this case,

no Bs1 signal expected.

C.M. Momentum of K in B*K decay

C.M. momentum of K in B K decay


Results BResults Bss**Results BResults Bss**

MeVstat

statN

MeVsyststatBM

MeVsyststatKMBMBM

s

s

.)(5.17.4

.)(31135

)(6.1)(4.11.5839)(

)(5.1)(3.14.66)()()(*2

*2

.)(0.94.36)(

)(6.0)(14.0)(21.041.5829)(

)(14.0)(21.073.10)()()(

.)(4.238.94)(

)(5.0)(14.0)(39.05839)(

)(14.0)(34.096.66)()()(

1

1

*1

*2

*2

*2

statBN

MeVPDGsyststatBM

MeVsyststatKMBMBM

statBN

MeVPDGsyststatBM

MeVsyststatKMBMBM

s

s

s

s

s

s

10.1 fbdtL

10.1 fbdtL


B Quest began … and continues @ FermilabB Quest began … and continues @ FermilabB Quest began … and continues @ FermilabB Quest began … and continues @ Fermilab

Celebrating 30 years of the b quark discovery @ Fermilab

A fitting anniversary celebration: Discovery of new B baryons…and the search goes on…!

1977

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08/09/2007 Tania Moulik, B Spectroscopy at Tevatron, ISMD 2007 1 International Symposium of...

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