# Presentation: 491340

## XXXVI International Meeting on Fundamental Physics

**Rick Field**
**University of Florida**
**(*****for the CDF & D0 Collaborations*****)**

**CDF Run 2**

***Palacio de Jabalquinto, Baeza, Spain***

** ****From IMFP2006 ****→ IMFP2008**** **

_**1**__**st**__** Lecture**_
**FF Phenomenology ****→ Tevatron ****Jet Physics**

- IMFP2008 - Day 1                                                  February 4, 2008

## The Fermilab Tevatron

**Fermi National Laboratory (****Fermilab****) is near Chicago, Illinois. ****CDF**** and ****D****Ø**** are the the two collider detector experiments at Fermilab.**

**Protons collide with antiprotons at a center-of-mass energy of *****almost***** ****2 TeV**** (actually 1.96 TeV).**

- IMFP2008 - Day 1                                                  February 4, 2008

## Tevatron Performance

**Luminosity records (IMFP 2008):**
**Highest Initial Inst. Lum: ~2.92****×10****32**** cm****-2****s****-1****    **
**Integrated luminosity/week: 45 pb****-1**
**Integrated luminosity/month: 165 pb****-1**

_**IMFP 2008**_
**~3.3 fb****-1**** delivered**
**~2.8 fb****-1**** recorded**

_**IMFP 2006**_
**~1.5 fb****-1**** delivered**
**~1.2 fb****-1**** recorded**

**Luminosity Records (IMFP 2006):**
**Highest Initial Inst. Lum: ~1.8****×10****32**** cm****-2****s****-1****    **
**Integrated luminosity/week: 25 pb****-1**
**Integrated luminosity/month: 92 pb****-1**

**~1.6 fb****-1**

**Integrated Luminosity per Year**

**The data collected since IMFP 2006 more than doubled **
**the total data collected in Run 2!**

- IMFP2008 - Day 1                                                  February 4, 2008

## Many New Tevatron Results!

**Observation of B****s****-mixing: Δm****s**** = 17.77 ****±**** 0.10 (stat) ****±**** 0.07(sys).**
**Observation of new baryon states: ********b**** and ********b.**
**Observation of new charmless: B****→****hh states.**
**Evidence for D****o****-D****o****bar mixing .**
**Precision W mass measurement: M****w**** = 80.413 GeV (****±****48 MeV).**
**Precision Top mass measurement: M****top**** = 170.5  (****±****2.2) GeV.**
**W-width measurement: 2.032 (****±0****.071) GeV.**
**WZ discovery (6-sigma): ******** = 5.0 (****±****1.7) pb.**
**ZZ evidence (3-sigma).**
**Single Top evidence (3-sigma) with 1.5 fb****-1****: ******** = 3.0 (****±****1.2) pb.**
**|V****tb****|= 1.02 ± 0.18 (exp) ± 0.07 (th).**
**Significant exclusions/reach on many BSM models.**
**Constant improvement in Higgs Sensitivity.**

**Some of the CDF Results since IMFP2006**

**I cannot possibility cover all the **
**great physics results from the**
**Tevatron since IMFP 2006!**

**I will show a few of the results!**

- IMFP2008 - Day 1                                                  February 4, 2008

## In Search of Rare Processes

- PRODUCTION CROSS **SECTION** (fb)

**1 pb**

**We are beginning to measure cross-sections ****≤**** 1 pb!**

- W’, Z’, T’

**We might get lucky!**

******(p****T****(jet) > 525 GeV) ****≈ 15 fb!**

**15 fb**

- IMFP2008 - Day 1                                                  February 4, 2008

## Toward and Understanding of Hadron-Hadron Collisions

**From 7 GeV/c ********0****’s to 600 GeV/c Jets.   The early days of trying to understand and simulate hadron-hadron collisions. **

**Feynman**

**and**

**Field**

**1****st**** hat!**

- IMFP2008 - Day 1                                                  February 4, 2008

## Hadron-Hadron Collisions

**What happens when two hadrons collide at high energy?**

**Most of the time the hadrons ooze through each other and fall apart (*****i.e.***** ****no hard scattering****).  The outgoing particles continue in roughly the same direction as initial proton and antiproton.**

**Occasionally there will be a ****large transverse momentum meson****.  ****Question: Where did it come from?**

**We assumed it came from quark-quark elastic scattering, but we did not know how to calculate it!  **

**Field-Feynman 1977 (preQCD)**

_**Feynman quote from FF1**_
**“****The model we shall choose is not a popular one,**
**so that we will not duplicate too much of the**
**work of others who are similarly analyzing **
**various models (e.g. constituent interchange **
**model, multiperipheral models, etc.).  We shall **
**assume that the high P****T**** particles arise from **
**direct hard collisions between constituent **
**quarks in the incoming particles, which **
**fragment or cascade down into several hadrons.”**

**“****Black-Box Model”**

- IMFP2008 - Day 1                                                  February 4, 2008

## Quark-Quark Black-Box Model

**Quark****-****Quark Black****-****Box Model**

**FF1 1977 (preQCD)**

_**Quark Distribution Functions**_
**determined from deep-inelastic**
**lepton-hadron collisions**

_**Quark Fragmentation Functions**_
**determined from e****+****e****-**** annihilations**

_**Quark-Quark Cross-Section**_
**Unknown! Deteremined from**
**hadron-hadron collisions.**

**No gluons!**

_**Feynman quote from FF1**_
**“****Because of the incomplete knowledge of **
**our functions some things can be predicted **
**with more certainty than others.  Those **
**experimental results that are not well **
**predicted can be “used up” to determine **
**these functions in greater detail to permit **
**better predictions of further experiments.  **
**Our papers will be a bit long because we **
**wish to discuss this interplay in detail.”**

- IMFP2008 - Day 1                                                  February 4, 2008

## Quark-Quark Black-Box Model

**Field-Feynman 1977 (preQCD)**

_**Predict**_
**particle ratios**

_**Predict**_
**increase with increasing **
**CM energy W**

_**Predict**_
**overall event topology**
**(FFF1 paper 1977)**

**“****Beam-Beam Remnants”**

**7 GeV/c ********0****’s!**

- IMFP2008 - Day 1                                                  February 4, 2008

## Feynman Talk at Coral Gables (December 1976)

**“****Feynman-Field **
**Jet Model”**

**1****st**** transparency**

**Last transparency**

- IMFP2008 - Day 1                                                  February 4, 2008

## QCD Approach: Quarks & Gluons

**FFF2 1978**

_**Parton Distribution Functions**_
**Q****2**** dependence predicted from QCD**

_**Quark & Gluon Fragmentation Functions**_
**Q****2**** dependence predicted from QCD**

_**Quark & Gluon Cross-Sections**_
**Calculated from QCD**

_**Feynman quote from FFF2**_
**“****We investigate whether the present **
**experimental behavior of mesons with **
**large transverse momentum in hadron-hadron **
**collisions is consistent with the theory of **
**quantum-chromodynamics (QCD) with **
**asymptotic freedom, at least as the theory **
**is now partially understood.”**

- IMFP2008 - Day 1                                                  February 4, 2008

## High PT Jets

**High P****T**** Jets**

**30 GeV/c!**

_**Predict**_
**large “jet” cross-section**

**Feynman, Field, & Fox (1978)**

**CDF (2006)**

**600 GeV/c Jets!**

_**Feynman quote from FFF**_
**“****At the time of this writing, there is **
**still no sharp quantitative test of QCD.**
**An important test will come in connection **
**with the phenomena of high P****T**** discussed here.”**

- IMFP2008 - Day 1                                                  February 4, 2008

## QCD Monte-Carlo Models:High Transverse Momentum Jets

**Start with the perturbative 2-to-2 (or sometimes 2-to-3) parton-parton scattering and add initial and final-state gluon radiation (in the leading log approximation or modified leading log approximation). **

**“****Underlying Event”**

**The “underlying event” consists of the “beam-beam remnants” and from particles arising from soft or semi-soft multiple parton interactions (MPI).**

**Of course the outgoing colored partons fragment into hadron “jet” and inevitably “underlying event” observables receive contributions from initial and final-state radiation.**

**The “underlying event” is an unavoidable background to most collider observables and having good understand of it leads to more precise collider measurements!**

- IMFP2008 - Day 1                                                  February 4, 2008

## Collider Coordinates

**The z-axis is defined to be the beam axis with the xy-plane being the “transverse” plane.**

******cm**** is the center-of-mass scattering angle and ******** is the azimuthal angle.  The “transverse” momentum of a particle is given by ****P****T**** = P cos(********cm****)****.**

|  | cm |
| --- | --- |
| 0 | 90o |
| 1 | 40o |
| 2 | 15o |
| 3 | 6o |
| 4 | 2o |

**Use ******** and ******** to determine the direction of an outgoing particle, where ******** is the “pseudo-rapidity” defined by ********= -log(tan(********cm****/2))****.**

**The “rapidity” is defined by ****y = log((E+p****z****)/(E-p****z****))/2**** and is equal to ******** in the limit E >> mc****2****.**

- IMFP2008 - Day 1                                                  February 4, 2008

## Quark & Gluon Jets

**The CDF calorimeter measures energy deposited in a cell of size ******** = 0.11****×****15****o****, whch is converted into ****transverse energy****, E****T**** = E cos(********cm****).**

**“****Jets”**** are defined to be clusters of transverse energy with a radius R in ********-******** space.  A “jet” is the representation in the detector of an outgoing parton (quark or gluon).**
**The sum of the E****T**** of the cells within a “jet” corresponds roughly to the E****T**** of the outgoing parton and the position of the cluster in the grid gives the parton’s direction.**

**Calorimeter Jets**

**Can also construct jets from the charged particles!**

- IMFP2008 - Day 1                                                  February 4, 2008

## Jets at Tevatron

**Experimental Jets: ****The study of “real” jets requires a “jet algorithm” and the different algorithms correspond to different observables and give different results!**

**Next-to-leading order parton level calculation**
**0, 1, 2, or 3 partons!**

**Experimental Jets: ****The study of “real” jets requires a good understanding of the calorimeter response!**

**Experimental Jets: ****To compare with NLO parton level (and measure structure functions) requires a good understanding of the “underlying event”!**

- IMFP2008 - Day 1                                                  February 4, 2008

## Jet Corrections

**Jet Corrections**

**Calorimeter Jets:**
**We measure “jets” at the “hadron level” in the calorimeter.**
**We certainly want to correct the “jets” for the detector resolution and effieciency.**
**Also, we must correct the “jets” for “pile-up”.**
**Must correct what we measure back to the true “particle level” jets!**

**Particle Level Jets:**
**Do we want to make further model dependent corrections?**
**Do we want to try and subtract the “underlying event” from the “particle level” jets.**
**This cannot really be done, but if you trust the Monte-Carlo models modeling of the “underlying event” you can try and do it by using the Monte-Carlo models (use PYTHIA Tune A).**

**Parton Level Jets:**
**Do we want to use our data to try and extrapolate back to the parton level?**
**This also cannot really be done, but again if you trust the Monte-Carlo models you can try and do it by using the Monte-Carlo models.**

**The ****“underlying event”**** consists of hard initial & final-state radiation plus the “beam-beam remnants” and possible multiple parton interactions.**

- IMFP2008 - Day 1                                                  February 4, 2008

## Inclusive Jet Cross Section (CDF)

**Inclusive Jet Cross Section (CDF)**

**Run 1 showed a possible excess at large jet E****T**** (see below).**
**This resulted in new PDF’s with more gluons at large x.**
**The Run 2 data are consistent with the new structure functions (CTEQ6.1M).**

**IMFP2006**

- IMFP2008 - Day 1                                                  February 4, 2008

## Inclusive Jet Cross Section (CDF)

**Inclusive Jet Cross Section (CDF)**

**IMFP2006**

**MidPoint Cone Algorithm           (R = 0.7, f****merge**** = 0.75)**
**Data corrected to the hadron level**
**L***** *****= 1.04 fb****-1**
**0.1 < |y****jet****| < 0.7**
**Compared with NLO QCD**

**Sensitive to UE + hadronization effects for P****T**** < 200 GeV/c!**

**today**

**1.13 fb****-1**

******(p****T**** > 525 GeV) ****≈ 15 fb!**

- IMFP2008 - Day 1                                                  February 4, 2008

## KT Algorithm

**kT Algorithm:**
**Cluster together calorimeter towers by their kT proximity.**
**Infrared and collinear safe at all orders of pQCD.**
**No splitting and merging.**
**No ad hoc Rsep parameter necessary to compare with parton level. **
**Every parton, particle, or tower is assigned to a “jet”.**
**No biases from seed towers.**
**Favored algorithm in e+e- annihilations!**

**K****T**** Algorithm**

**Only towers with E****T**** > 0.5 GeV are shown**

- Raw Jet ET = 533 GeV

- Raw Jet ET = 618 GeV

**Will the K****T**** algorithm be effective in the collider environment where there is an “underlying event”? **

**CDF Run 2**

- IMFP2008 - Day 1                                                  February 4, 2008

## KT Inclusive Jet Cross Section (CDF)

**K****T**** Algorithm (D = 0.7)**
**Data corrected to the hadron level**
**L***** *****= 385 pb****-1**
**0.1 < |y****jet****| < 0.7**
**Compared with NLO QCD.**

**IMFP2006**

**today**

**1.0 fb****-1**

**Sensitive to UE + hadronization effects for P****T**** < 200 GeV/c!**

- IMFP2008 - Day 1                                                  February 4, 2008

## High x Gluon PDF

**High x Gluon PDF**

**Forward jets measurements put constraints on the high x gluon distribution!**

**Uncertainty on gluon PDF (from CTEQ6)**

- x

**Big uncertainty for high-x gluon PDF!**

**high x**

**low x**

**Forward Jets**

- IMFP2008 - Day 1                                                  February 4, 2008

## KT Forward Jet Cross Section (CDF)

**K****T**** Algorithm (D = 0.7).**
**Data corrected to the hadron level.**
**L**** = 385 pb****-1.**
**Five rapidity regions:**
** ****|y****jet****| < 0.1**
**0.1 < |y****jet****| < 0.7**
**0.7 < |y****jet****| < 1.1**
**1.1 < |y****jet****| < 1.6**
**1.6 < |y****jet****| < 2.1**
**Compared with NLO QCD**

**IMFP2006**

**today**

**1.0 fb****-1**

- IMFP2008 - Day 1                                                  February 4, 2008

## Forward Jet Cross Section (CDF)

**MidPoint Cone Algorithm              (R = 0.7, f****merge**** = 0.75)**
**Data corrected to the hadron level**
**L**** = 1.13 pb****-1.**
**Five rapidity regions:**
** ****|y****jet****| < 0.1**
**0.1 < |y****jet****| < 0.7**
**0.7 < |y****jet****| < 1.1**
**1.1 < |y****jet****| < 1.6**
**1.6 < |y****jet****| < 2.1**
**Compared with NLO QCD**

**1.0 fb****-1**

- IMFP2008 - Day 1                                                  February 4, 2008

## Inclusive Jet Cross Section (DØ )

**Inclusive Jet Cross Section (D****Ø**** )**

**MidPoint Cone Algorithm    (R = 0.7, f****merge**** = 0.5)**
**L***** *****= 378 pb****-1**
**Two rapidity bins**
**Highest P****T**** jet is 630 GeV/c**
**Compared with NLO QCD (JetRad, No R****sep****)**

**IMFP2006**

**Log-Log Scale!**

**today**

**0.9 fb****-1**

- IMFP2008 - Day 1                                                  February 4, 2008

## CDF versus DØ

**MidPoint Cone Algorithm    (R = 0.7, f****merge**** = 0.75)**
**CTEQ6.1M ******** = P****T****/2**

**MidPoint Cone Algorithm          (R = 0.7, f****merge**** = 0.5)**
**CTEQ6.1M ******** = P****T**
**Threshold corrections (2 loops)**

_**Inclusive Jet (CDF)**_

_**Inclusive Jet (D**__**Ø**__**)**_

**Without threshold corrections!**

- IMFP2008 - Day 1                                                  February 4, 2008

## DiJet Cross Section (CDF)

**MidPoint Cone Algorithm           (R = 0.7, f****merge**** = 0.75)**
**Data corrected to the hadron level**
**L***** *****= 1.13 fb****-1**
** ****|y****jet1,2****| < 1.0**
**Compared with NLO QCD**

**Sensitive to UE + hadronization effects!**

**CDF Run II Preliminary**

- IMFP2008 - Day 1                                                  February 4, 2008

## Inclusive Jet versus DiJet (CDF)

**MidPoint Cone Algorithm    (R = 0.7, f****merge**** = 0.75)**
**CTEQ6.1M ******** = P****T****/2**

**MidPoint Cone Algorithm    (R = 0.7, f****merge**** = 0.75)**
**CTEQ6.1M ******** = mean(P****T1****,P****T2****)**

_**Inclusive Jet (CDF)**_

_**DiJet (CDF)**_

- IMFP2008 - Day 1                                                  February 4, 2008

## CDF DiJet Event: M(jj) ≈ 1.4 TeV 

**E****T****jet1**** = 666 GeV  E****T****jet2**** = 633 GeV **
**E****sum**** = 1,299 GeV M(jj) = 1,364 GeV**

**M(jj)/E****cm**** ****≈ 70%!!**** **

**Exclusive p+p ****→ p+p+****e****+****+e****-**** (16 events)**
****** ****= 1.6 ****± 0.3 pb**

**CDF Run II**

- IMFP2008 - Day 1                                                  February 4, 2008

## “Towards”, “Away”, “Transverse”

**“****Towards”, “Away”, “Transverse”**

**Look at correlations in the azimuthal angle ********relative to the leading charged particle jet (|********| < 1) or the leading calorimeter jet (|********| < 2).**
**Define ****|********| < 60****o**** as “Toward”****, ****60****o**** < |******** < 120****o ****as “Transverse ”****, and ****|********| > 120****o**** as “Away”****.  Each of the three regions have area ******** = 2****×****120****o ****= 4********/3.**

_****__** **__**Correlations relative to the leading jet**_
**Charged particles p****T**** > 0.5 GeV/c |********| < 1**
**Calorimeter towers E****T**** > 0.1 GeV |********| < 1**

**“****Transverse” region is very sensitive to the “underlying event”!**

**Look at the charged particle density, the charged PTsum density and the ETsum density in all 3 regions!**

- IMFP2008 - Day 1                                                  February 4, 2008

## Event Topologies

**“****Leading Jet”**** events correspond to the leading calorimeter jet (MidPoint R = 0.7) in the region |********| < 2 with no other conditions.**

**“****Leading Jet”**

**“****Leading ChgJet”**** events correspond to the leading charged particle jet (R = 0.7) in the region |********| < 1 with no other conditions.**

**“****Charged Jet”**

**“****Back-to-Back Inc2J”**

**“****Back-to-Back Exc2J”**

**“****Back-to-Back Inclusive 2-Jet”**** events are selected to have at least two jets with Jet#1 and Jet#2 nearly “back-to-back” (********12**** > 150****o****) with almost equal transverse energies (P****T****(jet#2)/P****T****(jet#1) > 0.8) with no other conditions .**

**“****Back-to-Back Exclusive 2-Jet”**** events are selected to have at least two jets with Jet#1 and Jet#2 nearly “back-to-back” (********12**** > 150****o****) with almost equal transverse energies (P****T****(jet#2)/P****T****(jet#1) > 0.8) and P****T****(jet#3) < 15 GeV/c.**

**subset**

**subset**

_**CDF-QCD Data for Theory**_
**The goal is to produce data **
**(*****corrected to the particle level*****) **
**that can be used by the theorists **
**to tune and improve the QCD **
**Monte-Carlo models that are used **
**to simulate hadron-hadron collisions.**

**Rick Field & Craig Group**

- IMFP2008 - Day 1                                                  February 4, 2008

## Overall Totals (|| < 1)

**“****Leading Jet” **

**Overall Totals (|********| < 1)**

**Data at 1.96 TeV on the overall number of charged particles (p****T**** > 0.5 GeV/c, |********| < 1) and the overall *****scalar***** p****T**** sum of charged particles (p****T**** > 0.5 GeV/c, |********| < 1) and the overall *****scalar***** ET sum of all particles (|********| < 1) for “leading jet” events as a function of the leading jet p****T****. The data are corrected to the particle level (*****with errors that include both the statistical error and the systematic uncertainty*****) and are compared with PYTHIA Tune A at the particle level (*****i.e.***** generator level)..**

**Nchg = 30 **

**PTsum = 190 GeV/c **

**ETsum = 330 GeV **

**ETsum = 775 GeV! **

- IMFP2008 - Day 1                                                  February 4, 2008

## “Towards”, “Away”, “Transverse”

**“****Leading Jet” **

**“****Towards”, “Away”, “Transverse”**

**Data at 1.96 TeV on the density of charged particles, dN/d********d********, with p****T**** > 0.5 GeV/c and |********| < 1 for “leading jet” events as a function of the leading jet p****T**** for the ****“toward”****, ****“away”****, and ****“transverse”**** regions.  The data are corrected to the particle level (*****with errors that include both the statistical error and the systematic uncertainty*****) and are compared with PYTHIA Tune A at the particle level (*****i.e.***** generator level).**

**Data at 1.96 TeV on the charged particle *****scalar***** p****T**** sum density, dPT/d********d********, with p****T**** > 0.5 GeV/c and |********| < 1 for “leading jet” events as a function of the leading jet p****T**** for the ****“toward”****, ****“away”****, and ****“transverse”**** regions.  The data are corrected to the particle level (*****with errors that include both the statistical error and the systematic uncertainty*****) and are compared with PYTHIA Tune A at the particle level (*****i.e.***** generator level).**

**Data at 1.96 TeV on the particle *****scalar***** E****T**** sum density, dET/d********d********, for |********| < 1 for “leading jet” events as a function of the leading jet p****T**** for the ****“toward”****, ****“away”****, and ****“transverse”**** regions.  The data are corrected to the particle level (*****with errors that include both the statistical error and the systematic uncertainty*****) and are compared with PYTHIA Tune A at the particle level (*****i.e.***** generator level).**

**Factor of ~4.5**

**Factor of ~16**

**Factor of ~13**

- IMFP2008 - Day 1                                                  February 4, 2008

## The “Toward” Region

**“****Leading Jet” **

**The “Toward” Region**

**Data at 1.96 TeV on the density of charged particles, dN/d********d********, with p****T**** > 0.5 GeV/c and |********| < 1 for “leading jet” events as a function of the leading jet p****T**** for the ****“toward”**** region.  The data are corrected to the particle level (*****with errors that include both the statistical error and the systematic uncertainty*****) and are compared with PYTHIA Tune A and HERWIG (without MPI) at the particle level (*****i.e.***** generator level).**

**Data at 1.96 TeV on the charged *****scalar***** p****T**** sum density, dPT/d********d********, with p****T**** > 0.5 GeV/c and |********| < 1 for “leading jet” events as a function of the leading jet p****T**** for the ****“toward”**** region.  The data are corrected to the particle level (*****with errors that include both the statistical error and the systematic uncertainty*****) and are compared with PYTHIA Tune A and HERWIG (without MPI) at the particle level (*****i.e.***** generator level).**

**Data at 1.96 TeV on the *****scalar***** E****T**** sum density, dET/d********d********, with |********| < 1 for “leading jet” events as a function of the leading jet p****T**** for the ****“toward”**** region.  The data are corrected to the particle level (*****with errors that include both the statistical error and the systematic uncertainty*****) and are compared with PYTHIA Tune A and HERWIG (without MPI) at the particle level (*****i.e.***** generator level).**

- IMFP2008 - Day 1                                                  February 4, 2008

## The “Away” Region

**“****Leading Jet” **

**The “Away” Region**

**Data at 1.96 TeV on the density of charged particles, dN/d********d********, with p****T**** > 0.5 GeV/c and |********| < 1 for “leading jet” events as a function of the leading jet p****T**** for the ****“away”**** region.  The data are corrected to the particle level (*****with errors that include both the statistical error and the systematic uncertainty*****) and are compared with PYTHIA Tune A and HERWIG (without MPI) at the particle level (*****i.e.***** generator level).**

**Data at 1.96 TeV on the charged *****scalar***** p****T**** sum density, dPT/d********d********, with p****T**** > 0.5 GeV/c and |********| < 1 for “leading jet” events as a function of the leading jet p****T**** for the ****“away”**** region.  The data are corrected to the particle level (*****with errors that include both the statistical error and the systematic uncertainty*****) and are compared with PYTHIA Tune A and HERWIG (without MPI) at the particle level (*****i.e.***** generator level).**

**Data at 1.96 TeV on the *****scalar***** E****T**** sum density, dET/d********d********, with |********| < 1 for “leading jet” events as a function of the leading jet p****T**** for the ****“away”**** region.  The data are corrected to the particle level (*****with errors that include both the statistical error and the systematic uncertainty*****) and are compared with PYTHIA Tune A and HERWIG (without MPI) at the particle level (*****i.e.***** generator level).**

- IMFP2008 - Day 1                                                  February 4, 2008

## The “Transverse” Region

**“****Leading Jet” **

**The “Transverse” Region**

**Data at 1.96 TeV on the density of charged particles, dN/d********d********, with p****T**** > 0.5 GeV/c and |********| < 1 for “leading jet” events as a function of the leading jet p****T**** for the ****“transverse”**** region.  The data are corrected to the particle level (*****with errors that include both the statistical error and the systematic uncertainty*****) and are compared with PYTHIA Tune A and HERWIG (without MPI) at the particle level (*****i.e.***** generator level).**

**Data at 1.96 TeV on the charged *****scalar***** p****T**** sum density, dPT/d********d********, with p****T**** > 0.5 GeV/c and |********| < 1 for “leading jet” events as a function of the leading jet p****T**** for the ****“transverse”**** region.  The data are corrected to the particle level (*****with errors that include both the statistical error and the systematic uncertainty*****) and are compared with PYTHIA Tune A and HERWIG (without MPI) at the particle level (*****i.e.***** generator level).**

**Data at 1.96 TeV on the *****scalar***** E****T**** sum density, dET/d********d********, with |********| < 1 for “leading jet” events as a function of the leading jet p****T**** for the ****“transverse”**** region.  The data are corrected to the particle level (*****with errors that include both the statistical error and the systematic uncertainty*****) and are compared with PYTHIA Tune A and HERWIG (without MPI) at the particle level (*****i.e.***** generator level).**

**Data at 1.96 TeV on the charged particle average p****T****, with p****T**** > 0.5 GeV/c and |********| < 1 for “leading jet” events as a function of the leading jet p****T**** for the ****“transverse”**** region.  The data are corrected to the particle level (*****with errors that include both the statistical error and the systematic uncertainty*****) and are compared with PYTHIA Tune A and HERWIG (without MPI) at the particle level (*****i.e.***** generator level).**

**Data at 1.96 TeV on the charged particle maximum p****T****, with p****T**** > 0.5 GeV/c and |********| < 1 for “leading jet” events as a function of the leading jet p****T**** for the ****“transverse”**** region.  The data are corrected to the particle level (*****with errors that include both the statistical error and the systematic uncertainty*****) and are compared with PYTHIA Tune A and HERWIG (without MPI) at the particle level (*****i.e.***** generator level).**

- IMFP2008 - Day 1                                                  February 4, 2008

## The “Transverse” Region

**“****Leading Jet” **

**The “Transverse” Region**

**Data at 1.96 TeV on the density of charged particles, dN/d********d********, with p****T**** > 0.5 GeV/c and |********| < 1 for “leading jet” events as a function of the leading jet p****T**** for the ****“transverse”**** region.  The data are corrected to the particle level (*****with errors that include both the statistical error and the systematic uncertainty*****) and are compared with PYTHIA Tune A and HERWIG (without MPI) at the particle level (*****i.e.***** generator level).**

**Shows the Data - Theory for the density of charged particles, dN/d********d********, with p****T**** > 0.5 GeV/c and |********| < 1 for “leading jet” events as a function of the leading jet p****T**** for the ****“transverse”**** region for PYTHIA Tune A and HERWIG (without MPI).**

**0.1 density corresponds to 0.42 charged particles in the “transverse” region!**

- IMFP2008 - Day 1                                                  February 4, 2008

## The “Transverse” Region

**“****Leading Jet” **

**The “Transverse” Region**

**Data at 1.96 TeV on the charged *****scalar***** p****T**** sum density, dPT/d********d********, with p****T**** > 0.5 GeV/c and |********| < 1 for “leading jet” events as a function of the leading jet p****T**** for the ****“transverse”**** region.  The data are corrected to the particle level (*****with errors that include both the statistical error and the systematic uncertainty*****) and are compared with PYTHIA Tune A and HERWIG (without MPI) at the particle level (*****i.e.***** generator level).**

**Shows the Data - Theory for the charged *****scalar***** p****T**** sum density, dPT/d********d********, with p****T**** > 0.5 GeV/c and |********| < 1 for “leading jet” events as a function of the leading jet p****T**** for the ****“transverse”**** region for PYTHIA Tune A and HERWIG (without MPI).**

**0.1 density corresponds to 420 MeV/c in the “transverse” region!**

- IMFP2008 - Day 1                                                  February 4, 2008

## The “Transverse” Region

**“****Leading Jet” **

**The “Transverse” Region**

**Data at 1.96 TeV on the *****scalar***** E****T**** sum density, dET/d********d********, with |********| < 1 for “leading jet” events as a function of the leading jet p****T**** for the ****“transverse”**** region.  The data are corrected to the particle level (*****with errors that include both the statistical error and the systematic uncertainty*****) and are compared with PYTHIA Tune A and HERWIG (without MPI) at the particle level (*****i.e.***** generator level).**

**Shows the Data - Theory for the *****scalar***** E****T**** sum density, dET/d********d********, with |********| < 1 for “leading jet” events as a function of the leading jet p****T**** for the ****“transverse”**** region for PYTHIA Tune A and HERWIG (without MPI).**

**0.4 density corresponds to 1.67 GeV in the “transverse” region!**

- IMFP2008 - Day 1                                                  February 4, 2008

## The Leading Jet Mass

**“****Leading Jet” **

**The Leading Jet Mass**

**Data at 1.96 TeV on the ****leading jet invariant mass**** for “leading jet” events as a function of the leading jet p****T****.  The data are corrected to the particle level (*****with errors that include both the statistical error and the systematic uncertainty*****) and are compared with PYTHIA Tune A and HERWIG (without MPI) at the particle level (*****i.e.***** generator level).**

**Shows the Data - Theory for the ****leading jet invariant mass**** for “leading jet” events as a function of the leading jet p****T**** for PYTHIA Tune A and HERWIG (without MPI).**

**Off by ~2 GeV**

- IMFP2008 - Day 1                                                  February 4, 2008

## The “Transverse” Region

**“****Leading Jet” **

**The “Transverse” Region**

**Shows the generator level predictions for the charged fraction, PTsum/ETsum, for PTsum (all p****T****, |********| < 1) and ETsum (all p****T****, |********| < 1) and for PTsum (p****T**** > 0.5 GeV/c, |********| < 1) and ETsum (all p****T****, |********| < 1)  for “leading jet” events as a function of the leading jet p****T**** for the ****“transverse”**** region from PYTHIA Tune A and HERWIG (without MPI).**

**Data at 1.96 TeV on the charged fraction, PTsum/ETsum, for PTsum (p****T**** > 0.5 GeV/c, |********| < 1) and ETsum (all p****T****, |********| < 1) for “leading jet” events as a function of the leading jet p****T**** for the ****“transverse”**** region.  The data are corrected to the particle level (*****with errors that include both the statistical error and the systematic uncertainty*****) and are compared with PYTHIA Tune A and HERWIG (without MPI) at the particle level (*****i.e.***** generator level).**

**P****T****(min) = 0 ****→ 0.5 GeV/c**

- IMFP2008 - Day 1                                                  February 4, 2008

## bb DiJet Cross Section (CDF)

**b-quark tag based on displaced vertices. Secondary vertex mass discriminates flavor.**

**Require two secondary vertex tagged b-jets within  |y|< 1.2 and study the two b-jets (M****jj****, ********jj****, etc.).**

**Collision point **

**≈**** ****85% purity! **

- IMFP2008 - Day 1                                                  February 4, 2008

## The Sources of Heavy Quarks

**We do not observe c or b quarks directly.  We measure ****D-mesons ****(which contain a c-quark) or we measure ****B-mesons**** (which contain a b-quark) or we measure ****c-jets**** (jets containing a D-meson) or we measure ****b-jets**** (jets containing a B-meson).**

**Leading Order Matrix Elements**

**Leading-Log Order**
**QCD Monte-Carlo Model (****LLMC****)**

**(structure functions)**

**× ****(matrix elements)**

**× ****(Fragmentation)**

**+ (initial and final-state radiation: LLA)**

- IMFP2008 - Day 1                                                  February 4, 2008

## Other Sources of Heavy Quarks

**In the leading-log order Monte-Carlo models (LLMC) the separation into ****“flavor creation”****, ****“flavor excitation”****, and ****“gluon splitting”**** is unambiguous, however at next to leading order the same amplitudes contribute to all three processes!**

_**Next to Leading Order Matrix Elements**_

**“****Flavor**** Excitation”**** (LLMC) corresponds to the scattering of a b-quark (or bbar-quark) out of the initial-state into the final-state by a gluon or by a light quark or antiquark.**

**“****Gluon-Splitting”**** (LLMC) is where a b-bbar pair is created within a parton shower or during the the fragmentation process of a gluon or a light quark or antiquark.  Here the QCD hard 2-to-2 subprocess involves only gluons and light quarks and antiquarks. **

**+**

**+**

**2**

_**and there are interference terms!**_

- IMFP2008 - Day 1                                                  February 4, 2008

## bb DiJet Cross Section (CDF)

**E****T****(b-jet#1) > 35 GeV, E****T****(b-jet#2) > 32 GeV, |********(b-jets)| < 1.2.**

_**Preliminary CDF Results:**_

******bb**** = 34.5 ******** 1.8 ****** **10.5 nb**

_**QCD Monte-Carlo Predictions:**_

| PYTHIA Tune A CTEQ5L | 38.7 ± 0.6 nb |
| --- | --- |
| HERWIG CTEQ5L | 21.5 ± 0.7 nb |
| MC@NLO | 28.5 ± 0.6 nb |
| MC@NLO + Jimmy | 35.7 ± 2.0 nb |

**Differential Cross Section as a function of the b-bbar DiJet invariant mass!**

**Adding multiple parton interactions (*****i.e.***** JIMMY) to enhance the “underlying event” increases the b-bbar jet cross section!**

_**JIMMY: MPI**_
**J. M. Butterworth**
**J. R. Forshaw**
**M. H. Seymour**

_**JIMMY**_
**Runs with HERWIG and adds multiple parton interactions!**

**IMFP2006**

- IMFP2008 - Day 1                                                  February 4, 2008

## bb DiJet Cross Section (CDF)

**E****T****(b-jet#1) > 35 GeV,                       E****T****(b-jet#2) > 32 GeV,  |********(b-jets)| < 1.2.**

**Sensitive to the “underlying event”!**

_**Preliminary CDF Results:**_

******bb**** = 5664 ******** 168 ******** 1270** **pb**

_**QCD Monte-Carlo Predictions:**_

| PYTHIA Tune A CTEQ5L | 5136 ± 52 pb |
| --- | --- |
| HERWIG CTEQ5L+Jimmy | 5296 ± 98 pb |
| MC@NLO+Jimmy | 5421 ± 105 nb |

**Systematic**
**Uncertainty**

**Predominately Flavor creation!**

- IMFP2008 - Day 1                                                  February 4, 2008

## bb DiJet  Distribution (CDF)

**It takes NLO + “underlying event” to get it right!**

**Large ******** (*****i.e.***** b-jets are “back-to-back”) is predominately “flavor creation”.**

**Small ******** (*****i.e.***** b-jets are near each other) is predominately “flavor excitation” and “gluon splitting”.**

- IMFP2008 - Day 1                                                  February 4, 2008

## Z + b-Jet Production (CDF)

**Important background for new physics!**

**Extract fraction of b-tagged jets from secondary vertex mass distribution: ****NO**** assumption on the charm content. **

***L***** = 335 pb****-1**

**Leptonic decays for the Z.**
**Z associated with jets.**
**CDF: JETCLU, D0:**
**R = 0.7, |********jet****| < 1.5, E****T**** >20 GeV**
**Look for tagged jets in Z events.**

**IMFP2006**

| Observable | CDF Data | PYTHIA Tune A | MCFM NLO (+UE) |
| --- | --- | --- | --- |
| (Z+b-jet) | 0.94±0.15±0.15 pb | -- | 0.51 (0.56) pb |
| (Z+b-jet)/(Z) | 0.369±0.057±0.055 % | 0.35% | 0.21 (0.23) % |
| (Z+b-jet)/(Z+jet) | 2.35±0.36±0.45 % | 2.18% | 1.88 (1.77) % |

**today**

**1.5 fb****-1**

**Sensitive to the “underlying event”!**

- IMFP2008 - Day 1                                                  February 4, 2008

## XXXVI International Meeting on Fundamental Physics

**Rick Field**
**University of Florida**
**(*****for the CDF & D0 Collaborations*****)**

**CDF Run 2**

***Palacio de Jabalquinto, Baeza, Spain***

** ****From IMFP2006 ****→ IMFP2008**** **

_**2**__**nd**__** Lecture (Tomorrow)**_
**Bosons, Top, and Higgs**

- IMFP2008 - Day 1                                                  February 4, 2008