# Presentation: 113027

## Charm Studies at CDF 

Burkard C. Reisert

for the CDF Collaboration

- Burkard C. Reisert
- for the CDF Collaboration

- • Charm Meson Pair Production
- •  Studies of Charmonium Production
- 	- J/and ' polarization
- 	- Relativec1, c2 Production

- Picture
- of
- FNAL
- or
- Oxford

## Motivation:Inclusive Charm Meson Cross Sections

***Motivation:******Inclusive Charm Meson Cross Sections***

**D****0**

***Kniehl *****et al., *****hep-ph/0508129***

- The measurement of inclusive charm meson\cross sections (D0, D*±, D+, Ds+) was one of the first CDF Run II results
-  up to a factor 2 higher than expected
-  progress in theory reduced deviation              - still on the high side
-  measurement systematically limited

**(L=5.8 pb-1)**

**CDF Run II (L=5.8 pb****-1****)**

**CDF Run II (L=5.8 pb****-1****)**

**FONLL**

***Cacciari *****et al., *****JHEP, 05:00, 1998***

*CDF Collab., PRL 241804*** **

## Heavy Quark Production: Leading Order Picture

***Heavy Quark Production: ******Leading Order Picture***

- Second charm particle in the event gives access to the underlying production mechanism
- Study fully reconstructed prompt charm meson pairs allows for acceptance and efficiency correction

**PS = Parton Shower**

## Charm Meson Pair Reconstruction

- Simple experimental approach
- Find triggered charm meson                  D0, D+, D*, Ds+,
- Look for second charm meson          probe D*+
- Take advantage of  inclusive measurement from a short well controlled running period:
-  Measure of pair cross section relative to inclusive cross section, systematic uncertainties largely cancel over the entire CDF Run II

**Primary**
**Vertex**

## Prompt Charm Production Cross Sections

- Inclusive production (already measured by CDF):
- Pair production:
- Relative pair Cross section:
- uses

*N**i*:	Number of observed charm mesons in *i**th*  *P**T* bin
*N**ij*:  Number of observed charm meson pairs with *D**1* in *i**th*  *P**T* bin and *D**2* in *j**th*  *P**T* bin
*f**P**D*: fraction of prompt D mesons
*f**P**DD*: fraction of prompt pairs
***i*:   trigger and reconstruction efficiency
***ij*:	pair trigger and reconstruction efficiency
***j*:	probe-side reconstruction efficiency
- d*t*: integrated luminosity
*B*: 	branching fraction e.g. *D**0****K***

## Inclusive triggered charm mesons

## Number of D0TrigD*±Probe Pairs

- 2dim SB-subtraction by weighting events
- In mass plane of **Trigger D** and
- soft  tagged **Probe D****0**

## Number of D0TrigD*±Probe Pairs

- 2dim SB-subtraction by weighting events
- In mass plane of **Trigger D** and
- soft  tagged **Probe D****0**

## Ds+D*- 

***D*******+******D*******-****** ***

***D******+******D*******-****** ***

## Charm Meson Pairs vs. (Raw Yields)

- Uncorrected for efficiency (**) and secondary (fb) detector level  distributions
- fully reconstructed decays of both D  correct for ** (simulation verified on data)

- D0D*-

- D0D*-

- D+D*-

- D0D*-

## Extraction of Prompt D Production

- Extract prompt/secondary fractions from Ip of  probe side D0: fbb =34%
- Cross checks : Ip, Lxy of trigger/probe D and DD*- pair

- Secondary D

- Prompt D

- PV = Primary Vertex

- Ip

## Measurement of  Charm Meson Pair Cross Section

- published CDF measurements
- of inclusive cross sections

- branching
- fraction
- from PDG

- Efficiency for fully
- reconstructed
- Probe side D*+

- Inclusive Charm Meson
- Yields and prompt
- Fractions

- DD Pair yields and
- Prompt fraction

## D0D*- Pair Cross Section  binned in PT(Trig) 

- Error:
- statsys(fb)
- Common
- Syst. Error:
- ~15%

## D0D*- Cross Section

-  Normalization of D0D*- cross section in Pythia is about right,
-  Gluon Splitting as important as Flavour Creation
-  Pythia  under estimates GS (over estimates FC)

## D+D*- Pair Cross Section binned in PT(Trig) 

- statsys(fb)
- Common
- Syst. Error:
- ~19%

- Significant shape discrepancy Consistent for *D**0**D***-* and *D**+**D***-*

***D******+******D*******-****** Pair Cross Section binned in P******T******(Trig) ***

## Charmonium Production

## Color Singlet & Color Octet models

- Color Singlet Model:
- cc pair is “bleached” by radiating off a hard gluon
- Underestimates J/ (1/10) and
- 	’ (1/50) production
- Feed down from cj dominates (>90%) J/ production
- 	(CDF Run I finds 30%)
- PT spectrum does not match data

- p

- p

- p

- J/

- J/

- hard g

- soft g

- c

- c

- c

- c

- Non relativistic QCD introduces
- Color Octet Mechanism:
- Soft gluon radiation
- Adjustable hadronization parameter allows to match the observed PT spectra and production cross sections
- Predicts transverse polarization for J/deviates from data

## “Pomeronic Idea”

- J/

- p

- Pomeron picture

- pQCD

- Recent idea by V.A. Khoze, A.D. Martin, M.G. Ryskin and  W.J. Sterling hep-ph/0410020
- Fusion of a symmetric colour octet state and a gluon
- Cross sections calculated in    LO pQCD consistent with data
- PT spectra match data
- Predicts longitudinal polarisation of J/increasing with pT

- Emission of    omerons
-    omerons have vacuum
- Quantum numbers JP = 00

## Polarization of J/

*** angle between + in J/ rest frame and J/ in lab frame
- polarization parameter
- 	=0 all 3 helicity states are equally populated
-  MC polarization templates
- 	(trigger efficiency from data)

## J/ Yields and Separation of Prompt and Secondary J/

***J/************ Yields and ******Separation of Prompt and Secondary J/*********

- Use  combined
- impact parameter
- significance to
- separate prompt S≤8
- and secondary S>16

- J/ selection
- Central: |y|<0.6
- 5<PT<30GeV/c

## Polarization of J/ Mesons

- Polarization of J/ from B decays
- independent of PT
- B = -0.066±0.050
- Consistent with BaBar
- 	(B = -0.129±0.009)
- CDF result includes *B**s* and *B* baryons

- Polarization of prompt J/
- Corrected for residual   secondary J
- <0: longitudinal polarization

## ’ Polarization 

- Same theoretical framework applies to prompt ’ and J/production
- no contribution from feed down from higher states therefore ’ is a cleaner system to test direct charmonium production
-  ’ uses analysis approach as just described for J/

## ’ Polarization Results

- Polarization of prompt ’
- Longitudinal polarization at high pT, just as for J/

- Polarization in B decays
- First measurement of B for ’
- B = 0.28±0.27± 0.03
- 	(consistent with J/ within stat.)

## cJ  Production

- Models of prompt charmonium production in hadron collisions always contain significant cJ contributions
- The measurement of (c2)/ (c1) has been performed at several energies and beam types over the years.
- Best measurements have ~100 events, 30% statistical uncertainty on the cross section ratio.
- Results like 1.0±0.3 are consistent with most models.

## Measurement of (c2)/(c1)

- Measurement of properties of cJ production has always been an experimental challenge
- Low energy photon from cJJ/ is difficult to measure (~400 MeV in cJ rest frame)
- Calorimeter measurements have  good efficiency but poor resolution and high background in a hadron collider environment
- Conversion measurement
- 	- good resolution
- 	- poor efficiency
-      (now compensated L=1fb-1)

## cJ Data Set

- Here we reconstruct:
- cJJ/, J/+-, e+e-
- J/ selection as polarization analysis
- Photon conversion gives excellent energy (mass) resolution.
- Prompt and B-decays are easily separated
- Simultaneous fit to the mass and flight
- distance distributions is used to extract
- the relative yields for both prompt cJ
- and cJ from *B* decays

## Results on c1)/c2)

- New level of precision    for measurement of c1**)/**c2**)**
- Should provide nice constraint on models of production mechanisms
- Result for prompt cJ:

- for 4 < pT(cJ) < 20 GeV/c

-  Color Octet predicts 5/3 (counting of Spin states)

## Conclusion 

- The unprecedented integrated luminosity delivered by the
- Tevatron in conjunction with CDF’s high bandwidth trigger
- allows us to perform Charm studies we did not anticipate.
- New “Charming” results:
- First measurement of charm meson pair cross section 	         in an hadron collider environment probes open charm production: gluon splitting underestimated
- Polarization measurements of J/ and ’ instigates              new theory approach to charmonium production
- New level of precision for measurement of (c1)/(c2) provides new trial to models of charmonium production
- Charm Physics at the Tevatron has its beauty

## Acknowledgements

- _Contact persons for the presented CDF analyses:_
- Charm meson pair cross Sections
- 	Burkard Reisert, _[reisert@fnal.gov](mailto:reisert@fnal.gov)_
*J*/ and ’ polarization
- 	Min-Jeong Kim _[mjkim@fnal.gov](mailto:mjkim@fnal.gov)_
- 	Kwangzoo Chung _[kchung@andrew.cmu.edu](mailto:kchung@andrew.cmu.edu)_
- Relative c1 c2 production
- 	Patrick Lukens _[ptl@fnal.gov](mailto:ptl@fnal.gov)_

## Backup slides

- Tevatron, CDF & Trigger

## Slide 31

## Slide 32

## Heavy Quark  Production in Higher Orders

- Example Feynman Diagrams
- Calculations with massive quarks
- incoming charm (?)
- charm in final
- 	state parton shower (?)
- All shown example graphs can be interpreted as higher order flavor creation

- Flavor Creation (a2s)

- Flavor Creation (a2s)

- Gluon Splitting (a3s)

- Flavor Excitation (a3s)

- Gluon Radiation (a3s)

- Interference Term (a4s)

- Interference Term (a4s)

- Gluon Radiation (a3s)

## Tevatron

***Tevatron***

**   ****Run II Physics Goals:**
-  Properties of top quark
-  Precision Electroweak Physics
-  CKM, *B**s* Mixing
-  Searches for new phenomena
-  Tests of QCD

- New world record

**ISR @ √s=62 GeV**

## Collider Detector at Fermilab

- Silicon Microstrip Tracker

- Time-of-Flight

- Drift Chamber

- Plug Calorimeter

- Muon

- Muon System

- Solenoid

- Central Calorimeter

- Fwd Calorimeter

**|********| to 5.5**

**Scint based |********| to 3.6**

**1.0<|********|<2.0**

- Old

- New

- Partially
- New

## CDF Trigger & DAQ System

- CDF Detector

- L1 trigger

- L2 trigger

- L3 farm

- disk/tape

*42 L1*
*buffers*

*4 L2*
*buffers*

- 1.7 MHz crossing rate

- 25 kHz L1 accept

- 500 Hz L2 accept

- 100 Hz L3 accept

- Hardware tracking for pT 1.5 GeV

- Refined Muon-track matching

- Electron-track matching

- Missing ET, sum-ET

- Silicon tracking

- Dedicated
- hardware

- Hardware +
- CPU

- Linux farm
- (>200 CPUs)

- Jet finding

- Full event reconstruction

- Refined electron/photon finding

- The trigger is the key to heavy
- flavour physics at hadron colliders

- Muon-track matching

## Triggers forBeauty & Charm Physics

- Di-Muon (*J*/****)
- PT(****) > 1.5 GeV
*J*/********(2S) modes
- Down to low PT(*J*/****)
- (~ 0 GeV)

- Two Track Trigger
- PT(trk)>2 GeV
- IP(trk) >100 ****m
- Fully hadronic modes

- Displaced track(s)
- + lepton (e,****)
- IP(trk)>120 ****m
- PT(lepton) >4GeV
- Semileptonic modes

******(2s), X(3872)******** *****J*****/********(quarkonia)**
**B****s*********J*****/********, B****u,d**** *****J*****/********K****s****(*)**** ********b*********J*********(masses, lifetimes, mixing calibration)**
**B****s,d************(rare decays)**
**B****c****(lifetime B*********J*****/********lX, mass B******** *****J*****/********)**

**2-body charmless decays (B****0****,B****s****,********b****)**
**B****s**** mixing (hadronic)**
**Charm physics **
**	****- inclusive cross sections**
**	****- D****0**********
**Heavy quark production**

**B****s**** mixing (semileptonic)**
**Tagging, lifetime**