PRESENT STATUS OF PHYSICS AT TEVATRON/CDF AND PROSPECTWITH HIGHER LUMINOSITY
Kazuhiro Yamamoto, Department of Physics, Osaka City University,
Osaka 558-8585, Japanfor the CDF collaboration
Abstract
The Tevatron Run II program is ongoing at Fermilab
with 1.96 TeV pp collisions. The upgrade from the Run I
system and the present status of the Tevatron and the CDF
are presented including some preliminary results obtainedin the Run II starting period. The future luminosity
prospects and the expected physics sensitivities are alsopresented.

• The bunch spacing was shortened from 3.5 µs to396 ns to maintain the number of interactions perbunch crossing properly.
The Recycler ring is currently under final integration, andit will be completed in 2003. In succession to Run IIa, theRun IIb program is planned with minor upgrades toward
the accumulation of 15 fb-1.

1 INTRODUCTION

3 THE CDF DETECTOR UPGRADE

The Tevatron collider has been providing pp collisions
at the world highest center-of-mass energy since the firstcollision in 1985. In Run I which was carried out from1992 through 1996, about 110 pb-1 of collision data werecollected at s =1.8 TeV using the CDF detector, andmany important results on particle physics were provided
including the direct observation of the top quark [1].
After the Run I operation, the Fermilab accelerators
were upgraded for Run II toward higher luminosity at theTevatron [2]. In parallel, the CDF detector was also
upgraded in order to allow operation at higher luminosity
collisions [3]. The Run IIa operation was started at a
center-of-mass energy of 1.96 TeV in March 2001. The
CDF II collaboration currently consists of 11 countries, 58
institutes, and about 600 physicists.

For the Tevatron Run II operation with high luminosity,
the substantial upgrades were needed to the CDF Run I
detector. We constructed the CDF II detector which isshown in Figure 1. The upgrade was made by replacing
the slow components with the fast ones and adding newcomponents to improve the detector capability. The
central tracking chamber has been replaced with a newcylindrical drift chamber (Central Outer Tracker, COT)
with smaller drift gaps. The silicon vertex detector has
been replaced with a new one (SVX II) with fasterreadout electronics and better radiation resistance. Theintermediate silicon layers (ISL) were newly added in thespace between SVX II and COT. The plug gas
calorimeters have been replaced with new scintillator tile
calorimeters which give much faster response. The timeof-flight detector (TOF) was added for better particle
identification at low energy. The coverage of the muon
detectors has been increased up to η ~ 1.5. Also all frontend and trigger electronics was re-designed for fast-speed

2 ACCELERATOR UPGRADE
The goal of the first phase of the Tevatron Run II (RunIIa) is to achieve a peak luminosity of 2 × 1032 cm-2s-1 andan integrated luminosity of 2 fb-1 at s = 1.96 TeV.
Among a number of upgrades which were made toaccomplish the above performance, the important changes
are as follows:• A high-intensity proton synchrotron (Main Injector)
was newly built as an injector of the Tevatron. It isalso used to produce anti-protons with the fixedtarget operation.
• A new storage ring (Recycler) was placed in thesame tunnel as the Main Injector to collect antiprotons left over at the end of a store and reuse themin the next store.
• The number of proton and anti-proton bunches in
the Tevatron ring was increased from 6 × 6 to 36 ×36.

Figure 1 : Schematic view of the CDF II detector

Figure 2 : The integrated luminosity delivered (uppercurve) and recorded (lower curve) by the CDF II
through October 14th, 2002.
processing. On the construction of the CDF II detector,
the large contribution was made by Japanese institutes tothe silicon detectors (SVX II and ISL), the end-plugcalorimeters, the time-of-flight detector, and the dataacquisition system. The installation of all the detector
components was successfully completed, and the new
CDF II detector was rolled into the collision hall in thefall of 2000.

4 EARLY RESULTS OF RUN IIA
After the half-year commissioning runs, the Run II
operation officially started in March 2001. Continuous
efforts by the Fermilab accelerator group are keeping theTevatron luminosity improving. The CDF II detector had
been also getting tuned, and it was in stable condition byFebruary 2002. As of October 2002, we are achieving thetypical peak luminosity of 2.5 ~ 3.0 × 1031 cm-2s-1 stably.
The integrated luminosity of 100 pb-1 has been delivered
and 70 pb-1 has been recorded so far as presented inFigure 2.

+ −Figure 3 : Invariant mass spectrum of Z → e ecandidates.

Figure 4 : Transverse mass spectrum of W → µν
candidates.
Using these data, the physics analysis is currently inprogress in parallel with various calibrations. Figure 3 and4 show the invariant mass spectrum of Z → e + e −candidates and the transverse mass spectrum of W → µν
candidates respectively. Both spectra are in good
agreement with the Monte Carlo simulations including theexpected background spectra. The W mass is extracted
from a fit to the transverse mass distribution of
W → eν and µν. The mass accuracy is expected to be ~30 MeV/c2 with 2 fb-1 in Run IIa, which is competitive tothe combined LEP2 result [4].
Figure 5 shows the invariant mass spectrum of
J/ψ → µµ candidates which was obtained byreconstructing low-pT muon pairs. The spectrum ofψ (2 S ) → µµ is also superimposed. By taking advantageof the large statistics of the J/ψ sample, it is used for
tracking calibration and momentum-scale adjustment.

Figure 5 : Invariant mass spectra of J/ψ → µµ andψ (2 S ) → µµ candidates.

Also, the J/ψ sample is a powerful tool to research B
physics. The mass spectrum of Bs0 obtained from+−reconstruction of J/ψ φ ( φ → K K ) is shown in Figure
6. The obtained mass accuracy is starting to becompetitive to the world average [5].

Figure 6 : Reconstructed mass distribution of+

B → J/ψ K+

candidates.

5 PHYSICS PROJECTIONS TO THE CDF
RUN IIAs written above, the integrated luminosity will reach 2
fb-1 in Run IIa and 15 fb-1 in Run IIb. Various physics
results are expected assuming the above statistics. One ofthe most important objectives in Run II is a research onthe top quark. By scaling up the yield obtained in Run I,
we expect to collect about 800 t t events by b-quark
tagging with 2 fb-1. The precise measurements of the topquark mass and the production cross section will be made.
The B physics is also expected to give us a greatoutcome during the Run IIa period [6]. The measurementof Bs0 − Bs0 mixing by means of Bs0 → Dsπ and Dsπππ
decay modes is being studied. As presented in Figure 7,
the CDF has the sensitivity to the 5σ discovery for xs (=∆ms / Γs) smaller then 60 with 2 fb-1. This measurement isa unique subject at the Tevatron, and complementary tomeasurements by other B-factory experiments. Also CPviolation in B 0 → J/ψ K S0 can be observed in terms ofthe measurement of sin2β with an accuracy of ~0.05.
As for the standard model Higgs search at the Tevatron,
the gluon fusion ( gg → h ) and the vector-boson
associated production ( qq ' → hW , qq → Zh ) are themain production processes. The predicted cross sections
are ranging from 1 to 0.1 pb. Concerning the decay mode,h → bb dominates in the low-mass region below 130
GeV/c2. Based on this prediction, the low-mass Higgs
search is being studied inFigure 7 : The expected accuracy of sin2β measurement and the expected sensitivity of xs for Bs0 − Bs0
mixing as a function of the integrated luminosity.

qq ' → Wh → lν bb
qq → Zh → l + l −bb , νν bb .
In order to discriminate the Higgs signal from the large
QCD background, we require high-pT leptons and/or
neutrinos (missing energy) for triggering the signal.
Studies to improve the b-tagging efficiency and the b-jet
reconstruction are in progress. For the high-mass Higgs
above 130 GeV/c2, since the decay h → WW becomesdominant, we search for+ −gg → h → WW * → l l vv
qq ' → Wh → l ±ν W *W * → l ±ν l ±ν jj± ∓± ∓ ±qq → Zh → l l W *W * → l l l ν jj
as the Higgs production signal. If the Higgs boson iscreated via the vector-boson associated production, wecan observe a like-sign dilepton which is rare in thestandard model background processes. Figure 8 shows therequired integrated luminosity either to exclude thestandard model Higgs at 95% C.L. limit, or to discover
the Higgs at the 3σ or 5σ level of significance as afunction of the Higgs mass. For the 120 GeV/c2 Higgs, it
can be excluded with 2 fb-1 if it does not exist. However,
if it exists, we can achieve the 3σ evidence with 7 fb-1 andthe 5σ discovery with 15 fb-1 [7].
Even if the standard model Higgs is not discovered, theconstraint on the Higgs mass can be set through theradiative correction of the top quark mass (Mtop) and theW boson mass (MW). The accuracies of MW and Mtop areexpected to be 30 MeV/c2 and 3 GeV/c2 with 2 fb-1 in Run
IIa, which corresponds to the Higgs mass (Mh) accuracyof 1/2Mh < Mh < 2Mh as shown in Figure 9. With 15 fb-1
in Run IIb, the Higgs mass will be determined with anaccuracy of 30% with improved accuracies of MW (30MeV/c2) and Mtop (2GeV/c2).

Figure 9 : The standard model prediction of the Higgs
mass dependence on the W mass and the top quark
mass. The expected accuracy in the CDF Run IIa (2 fb1) is superimposed.
Figure 8 : The required integrated luminosity either toexclude the standard model Higgs at 95% C.L. or to
discover it at the 3σ or the 5σ level as a function of theHiggs mass.

6 FUTURE PROSPECTS AND SUMMARYAs described in the previous sections, the Fermilab
accelerators and the collider detectors were successfullyupgraded, and the Tevatron Run IIa operation started inMarch 2001. The CDF detector is working well, and weare accumulating physics data of pp collisions with goodquality. Data analyses are also in progress. We expect tomaintain the peak luminosity of the Tevatron in the range
2.5 ~ 4 × 1031 cm-2s-1 in 2002, which will result in theintegrated luminosity about 150 pb-1. After the Recycler
installation and commissioning in 2003, the peakluminosity is expected to rise up to 4 ~ 6 × 1031 cm-2s-1.
The integrated luminosity will reach 2 fb-1 over 2 ~ 3years, which is 20 times larger statistics than weaccumulated in Run I.
The Run IIb program is planned with higher luminosity
after Run IIa. The peak luminosity of 4 × 1032 cm-2s-1 isexpected. The luminosity gain will be achieved mainly byincreasing the anti-proton intensity. The six-month shutdown is scheduled in 2005 to make some minor upgradesof the collider detectors. The silicon detector will bereplaced with the radiation-hard ones. The goal of the Run
IIb program is the luminosity accumulation of 15 fb-1
during 4 year running through 2008.

The Fermilab Tevatron collider will continue to explore
the high energy frontier of particle physics until the LHCstarts at CERN. It will provide unique opportunities todiscover the Higgs boson and to explore the physics
beyond the standard model. Also some early results are
already competitive to the world best accuracies in spiteof the low statistics. It is expected to give us a number ofimportant physics outputs such as the top-quark properties
and the CP structure in b mesons using the large statistics
through Run IIa and Run IIb.

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Conference on High Energy Accelerators, World
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[3] CDF Collaboration, “The CDF II Detector Technical
Design Report”, FERMILAB-Pub-96/390-E.
[4] The LEP Collaboration, LEPEWWG/2001-02, hepex/0112021 (2001).
[5] Particle Data Group, “Review of Particle Physics”,
Phys. Rev. D66 (2002) 010001.
[6] K. Anikeev et al., “B Physics at the Tevatron: Run IIand Beyond”, FERMILAB-Pub-01/197 (2001), hepph/0201071 (2002).
[7] The Tevatron Higgs Working Group, FERMILABConf-00/279-T (2000), hep-ph/0010338 (2000).