# Presentation: 861759

## The Run II Physics Program

**John Womersley**
**Fermi National Accelerator Laboratory, Batavia, Illinois**
**Representing the CDF and D****Ø collaborations**

## The Run II physics program

**A broad physics program which evolves as a function of luminosity**
**There is interesting physics at all luminosities, starting now with 50-100 pb****-1**** and continuing through 0.3, 1, 2, 5, 8 ... fb****-1**** **
**This physics program has begun**
**The goal of the collaborations is to **
_**Maximize**_** this physics program **
_**Exploit the full potential**_** of the world’s highest energy collider and the large investments we have made in the accelerator and detectors**
_**Lay a firm foundation**_** for the LHC and for future initiatives at the TeV scale **
- Attract and train the best students in the field
- Clarify physics requirements
- An international program in the US - groundwork for the future

## Big Questions at the Electroweak Scale

**Big Questions at the Electroweak Scale**

**The Tevatron is the only accelerator in operation that can help to answer **
**What is the structure and what are the symmetries of space-time?  **
**Why is the weak force weak?  **
**What is cosmic dark matter made of? **
**Run II is the only opportunity to make such a major discovery ****at an accelerator in the United States**

**About six to seven times more mass in the universe (27****±4%****) than there is baryonic matter (4.4****±0.4%****)**

**What is this stuff?  How****can we get a firmer ****understanding of it?**
**Accelerators**

## The program

**The Run II Physics program**
**Confront the standard model through precise measurements**
**The strong interaction, the quark mixing matrix, the****electroweak force and the top quark**
**Directly search for particles and forces not yet known **
**Both those predicted (Higgs, supersymmetry, dark matter, extra dimensions) and those that would come as a surprise**
**The program was developed in a series of workshops between 1998 and 2000**
_**[http://fnth37.fnal.gov/run2.html](http://fnth37.fnal.gov/run2.html)**_
**The program stretches from the GeV scale to the TeV scale**
**Here I can attempt only a superficial survey and will concentrate on the physics that gains most from luminosity**
**Illustration of the breadth of the program: ****110 talks from CDF and D****Ø at**** APS/DPF meeting in April**

## Two Worldwide Collaborations

**12 countries, 59 institutions**
**706 physicists**
**   **

**18 countries, 78 institutions**
**664 physicists**
**   **

**More than 50% non-US: a central part of the world HEP program **

**19**

**80**

**670**

**767**

## Analysis

****

**W ******** ******

**B****±**** lifetime**

**SVT triggered B-sample**

**First Run II Paper**

## Operations Status

**Both experiments are operating well and recording physics quality data with high (85-90%) efficiency **
**Data are being reconstructed within a few days **
**100-140 pb****-1**** with all detectors integrated is being used for physics analysis for summer 2003**

**D****Ø**

**Delivered   225 pb-1**
**Recorded  180 pb-1**
**(80%)**
**83% since February **

**Since Feb 10 2003, silicon in 94% of time**

**CDF**

## The Top Quark

**Why, alone among the elementary fermions, does the top quark couple strongly to the Higgs field?**
**Is nature giving us a hint here?**
**Is the mechanism of fermion mass generation indeed the ****same as that of EW symmetry breaking?**
**The top is a window to the origin of **_**fermion**_** masses**
**The Tevatron Collider is the world’s **_**only source of top quarks**_
**We are measuring its**
**Mass**
**Production cross section **
**Spin **
**Through top-antitop ****spin correlations**
**Electroweak properties**
**Through single top ****production**
**Any surprises, anomalies?**

**X ******** t+jet**

- E. Simmons

**The Run II Top Physics Program has begun**

##  -

*** ************-***

***MTC***

***IP***

***SV***

***IP***

***SV***

*** ******Jet 1***

*** ******Jet 2***

## The top quark rediscovered, 2003

*CDF dileptons **** =13.2 *±* 5.9**stat** *±* 1.5**sys** pb*
*CDF l + jets **** =5.3 *±* 1.9**stat** *±* 0.8**sys** *±* 0.8**lum**  pb*
*D**Ø (comb.)*

**CDF mass**

**Cross section**

## Top mass

**Top mass**

**We can look forward to improved precision on m****t**** in the near future**
**More data (few hundred pb****-1****)**
**Expect ~ 500 b-tagged lepton+jets events per experiment per fb****-1**
**cf. World total at end of Run I ~ 50**
**Improved techniques**
**e.g. new DØ Run I mass****measurement is equivalent****to a factor 2.4 increase****in statistics:**
**Improved top mass measurements help to constrain the Higgs mass**
**	****	********m****t ****	*****l *****+ jets****   ****	****       ****dilepton ****              **
**	****	****2 fb****-1****	****± 2.7 GeV   ± 2.8 GeV**
**	****	****5 fb****-1****	****± 2.2 GeV   ± 2.2 GeV**
**	****	**

*m**top*

- per experiment, using the “classic” technique

**dm****H****/dm****t**** ~ 50 GeV/4 GeV**

*[from M. Grunewald et al., hep-ph/0111217 (2001)]*

## Top physics program

**Top physics program**

**Precise knowledge of m****t**** (~1 GeV)****will be very useful even after a light ****Higgs is discovered**
**Is it H****SM**** or SUSY h?**
**Constrain the stop sector:**
*	**	**[M. Beneke et al., hep-ph/0003033]*
**Single top production**
**The way to measure top width**
**So far unobserved**
**With ~ 1 fb****-1**** should be able to see signals for both s and t-channel production (have different sensitivity to new physics)**
** ****	****	****	******** ****(s)****	********|V****tb****|(s) ****	******** (t)****	********|V****tb****|(t)**
**	****2 fb****-1**** ****	****21%****	****12%****	****	****12%****	****10%**
**	****5 fb****-1****	****13%****	****8%****	****	****8%****	****9%**
*	**[scaled from T. Stelzer, Z. Sullivan and S. Willenbrock, Phys. Rev. ****D58****, 094021 (1998)]*
**Top-antitop spin correlations **
**With 5fb****-1****, distinguish spin-****1⁄2 from spin-0 at the 3******** level**
**New physics****	**
******tt mass, top p****T****, rare decays and nonstandard decays, anomalous single top ...**

- h and stop1 discovered

## Electroweak Physics

**Electroweak Physics**

**In Run II we will complement direct searches for new phenomena with indirect probes**
**New particles and forces can be seen indirectly through their effects on electroweak observables. **
**Tightest constraints come from improved determination of the masses of the W and the top quark.  **
**Both experiments have preliminary results from Run  II samples of W and Z candidates:**

***Run II***

**D****Ø**
**Z ******** ******

**CDF**
**W ******** e******

## Prospects for W mass

**Prospects for W mass**

**Current knowledge of m****W**
**hadron colliders:**
**80 454 ****± 59 MeV**
**World (dominated by LEP)**
**80 451 ****± 33 MeV**
**Run II prospects **
- (per experiment)
**	****	********m****W**
**2 fb****-1****	****±27 MeV**
**5 fb****-1****	****±22 MeV**
- 	**We have shown we can measure the W mass precisely at the Tevatron, but to improve on LEP will require ~ fb****-1**** datasets - not a short term goal**

**dm****H****/dm****W**** ~ 50 GeV/25 MeV**

*[from M. Grunewald et al., hep-ph/0111217 (2001)]*

## Other electroweak measurements

**Other electroweak measurements**

**Forward-backward asymmetry A****FB**** in Z ******** ee**
**measure effective sin****2********W ****to 0.0004 (5 fb****-1****) and test *********/Z interference at ********s much greater than LEP**
**Other electroweak measurements**
**Multiboson production  (test gauge couplings)**
**Boson plus jets**
**...**

**CDF ****– ****Paper in preparation**

**Projection for 10 fb****-1**

## QCD

**No one doubts that QCD describes the strong interaction between quarks and gluons**
**Its effects are all around us:  **
**masses of hadrons (stars and planets)**
**But it is not an easy theory to work with**
**Use the Tevatron to **
**Test QCD itself**
**Understand some outstanding puzzles from Run I**
**Develop the expertise to calculate, and confidence in, the backgrounds to new physics**
**Excellent interaction between the experimental and phenomenology communities **

## Some QCD Physics goals for Run II

**Run I jet data already used in CTEQ6 and ****MRST2001 parton distribution fits;**
**complements HERA’s kinematic range**

**High p****T**** jets constrain the gluon content of the proton**

**b-jet cross section**
**Important background to new physics**

- Jets per GeV

## Jets in Run II

**Jets in Run II**

**B-jet cross section**

**Dijet mass**

- Prediction is pure PYTHIA to test  consistencywith Run I

**Inclusive**
**Jets**

## Searches for New Physics

**Searches for New Physics**

**The Tevatron, as the world’s highest energy collider, is the most likely place to directly discover a new particle or force**
**We know the SM is incomplete**
**Most popular extension: supersymmetry****	**
**Predicts multiple Higgs bosons, strongly interacting squarks and gluinos, and electroweakly interacting sleptons, charginos and neutralinos**
**masses depend on unknown parameters, ****expected to be 100 GeV - 1 TeV**
**Lightest neutralino is a good candidate for cosmic dark matter**
**Potentially discoverable at the Tevatron**

## Supersymmetry signatures

**Squarks and gluinos are the most copiously produced SUSY particles**
**As long as R-parity is conserved, cannot decay to normal particles **
**Jets plus missing transverse energy signatures**

**Missing E****T**
**SUSY ****	****        backgrounds**

**Make dark matter at the Tevatron!**

**Search region typically > 75 GeV**

**Detect its escape from the detector**

- Possible decay chains always end in the LSP

## Searching for squarks and gluinos

**Searching for squarks and gluinos**

**Run I**

**With 2 fb****-1****:**
**Reach in gluino mass ~ 400 GeV**

- CDF

## Chargino/neutralino production

**Chargino/neutralino production**

**“****Golden” signature**
**Three leptons**
**very low standard ****model backgrounds**
**This channel becomes ****increasingly important as ****squark/gluino production ****reaches its kinematic limits ****(masses ~ 500 GeV)**
**Reach on ************ mass, 2fb****-1****	**** ~ 180 GeV (tan ******** = 2, μ< 0)****	****	****	**** ~ 150 GeV (large tan ********) **
**	**

**A****0****=0, ********>0**
**2,**** ****10,**** ****30 fb****-1**

## Other Searches at the Tevatron

**Other Tevatron search channels ****for SUSY **
**GMSB ******** Missing E****T**** + photon(s)**
**Stop, sbottom**
**RPV signatures**
**Searches for other new phenomena **
**leptoquarks, dijet resonances, W’,Z’, massive stable particles, doubly charged particles...**

**CDF Run II Z’ > 650 GeV/c****2****  **

**Many search results now****comparable or better than Run I**

## Extra Dimensions

**Run II is also testing the new and exciting idea of extra dimensions**
**Can gravity propagate in more than four dimensions of space-time?**
**If these dimensions are not open to the other SM particles and forces, we would not perceive them**
**Particle physics experiments at the TeV scale could see effects (direct and indirect)**
**Measure the structure of space-time!**

**With 2 fb****-1****, we probe up to 2 TeV **

- DØ
- Run II
- Preliminary

## Signature-based searches

**	****We need to ensure that our searches are not constrained by our preconceptions of what might be “out there.”**

**Follow up anomalies in Run I data, and set model-independent limits**
**“****Sleuth” framework used very successfully by D****Ø***Phys. Rev. D {62} 92004 (2000)*** **

**CDF dilepton top events**

**Run I**

**Run II**

*There are more things in heaven and earth, Horatio, **Than are dreamt of in your philosophy.  *

**D****Ø ****Run II Preliminary**
**Limit on********pp ******** e******** + X**

**?**

## The Higgs Boson

**In the Standard model, the weak force is weak because the W and Z gain mass from a scalar field that fills the universe**
**The same field is responsible for the mass of the fundamental fermions**
**If it exists, we can excite the field and observe its quanta in the lab**
**The Higgs boson**
**Last piece of the SM**
**Key to understanding beyond-the-SM physics like supersymmetry: a light Higgs is a basic prediction of SUSY**
**All the properties of the Higgs are fixed in the SM with the exception of its own mass: simulations have no free parameters**

## Higgs Hunting at the Tevatron

**Higgs Hunting at the Tevatron**

**For any given Higgs mass, the production cross section and decays are all calculable within the Standard Model**
**Inclusive Higgs cross section is ****quite high: ~ 1pb**
**for masses below ~ 140 GeV,****the dominant decay is H ******** bb ****which is swamped by background**
**at higher masses, can use inclusive****production plus WW decays**
**The best bet below ~ 140 GeV appears ****to be associated production of H plus ****a W or Z**
**leptonic decays of W/Z help give ****the needed background rejection**
**cross section ~ 0.2 pb**

**H ********bb**

**H ******** WW**

**Dominant decay mode**

## Update on Higgs sensitivity

**A CDF + D****Ø joint study has now ****updated the “famous” Higgs reach plot:**
**Concentrated on low mass region (favored both in SM and SUSY)**
**The Higgs reach at the Tevatron appears to be at least as good as was projected four years ago**
**Our understanding will continue to improve**

**5******** ****discovery**
**3******** ****evidence**
**95% ****CL exclusion**

- Statistical power onlySystematics not included

## SUSY Higgs Production at the Tevatron

**SUSY Higgs Production at the Tevatron**

**bb(h/H/A) enhanced at large tan ********:**
****** ****~ 1 pb for tan******** = 30 and****m****h**** = 130 GeV**

**CDF Run I analysis (4 jets, 3 b tags) **
**sensitive to tan ******** > 60**

**Preliminary**

## What if we see nothing?

**	****Exclusion of a Higgs would itself be a very important result for the Tevatron**
**In the SM, can exclude the LEP “hint” (115 GeV) with ~ 2 fb****-1**
**The most interesting mass range with ~ 5 fb-1**
**Almost all the allowed mass range with ~ 10 fb****-1**

## Conclusions

**The Run II physics program has begun**
**We now have more data than Run I, taken at a higher CM energy with better detectors**
**The combination of highest accelerator energy, excellent detectors,  enthusiastic collaborations, and data samples that double every year guarantees interesting and important new physics results at every step.**
**Each step answers important questions, and each step leads on to the next.**
**The physics program gains from luminosity. It is worthwhile to push the luminosity as far as we can go.  But the program will be a success whatever level we reach.  **