# Presentation: 081212

## Status of BTeV 

- Joel Butler
- Fermilab
- Annual Fermilab Users’ Meeting
- June 10-11, 2002

## There has been dramatic progress recently in the Study of CP Violation

- KTeV  and NA48 have made a major advance in reducing the  statistical and systematic uncertainties in  ’/ and other CPV decays
- BaBar and Belle have conclusively established CP violation in B decays through their measurement of values of sin 2 that are many  from zero. They will continue to pursue CP violation in B decays in Bd and Bu for many years, eventually limited by the limited number of B’s they have
- Fermilab: Run II is expected to bring new results on Bs mixing and CP violation studies in a variety of Bd/u and Bs final states from CDF and D0

**After this phase,  there will still be much work to be done **
**and that is where BTeV will excel.**

## Wolfenstein Parameterization of the CKM Matrix 

-  is the imaginary piece of the CKM elements Vtd and Vub. _**According to the SM, **__****__**  is responsible for CP violation, in both Kaon and B  (and all other) decays**_**.** The smallest number of generations for which unitarity permits a weak phase is three generations.

- The CKM Matrix describes the mixing of the charge 1/3 quarks,
-  here to 3rd order in for real part and 5th order in imaginary part

-  **Is this description right? Is it complete?  Physics beyond the Standard Model could cause deviations from this picture.**

## The CPV Situation

- The Standard Model of CPV is _**unique, predictive, and testable**_
- CPV is one of the _**LEAST TESTED**_ aspects of the Standard Model
- Almost any _**EXTENSION**_ of the Standard Model _**has new sources of CPV**_
- The observed _**baryon asymmetry of the universe requires new sources of CPV**_ (not necessarily at this scale, though)

- It is “possible, likely, unavoidable”  that the SM picture of CPV is incomplete. CPV is an excellent probe for new physics. _It is testable._

**Conclusion: challenge SM CPV on every front. **

## Key Measurements of the CKM matrix in B Decays

**About 1/2 of the key measurements are in B****s**** decays!**
**About 1/2 of the key measurements have ********o****’s or ********’s**
**in  the final state!**

## Character of Proposed Experiments

**Sometime around 2008, Fermilab’s possession of the energy frontier will end after  20 years.**
**BTeV is aimed at New Physics, but to study it, focuses **
**on “the sensitivity frontier”  --areas where rate and efficiency are more important than energy**
**and where the energy difference between the Tevatron and the LHC is not critical**
**This should be viewed in the broader context of a program of  “flavor physics” which includes the study of kaon decays neutrino masses, mixing (MNS matrix), and CP violation**

**These experiments will address some of the most important problems in particle physics.**

##  Experiment R&D  

- The creation of a new experiment  is now almost always a big task
**At a mature machine whose energy is not growing, you are improving your reach by  doing much harder experiments which may require**
** ****running at much higher luminosity **
**achieving much higher background rejection**
- This may in turn mean developing new kinds of detectors, triggers,  or computing techniques or even new kinds of beamlines

**The development of a sophisticated new experiment and**
**the demonstration of its technical and scientific feasibility**
**is in itself a significant research project and needs support,**
**staffing, supervision,  review, and *****recognition.***

## B Physics at Hadron Colliders

**The Opportunity**
**The Tevatron****, at 10****32 ****, produces 10****11**** b-pairs per year**
**It is a “**_**Broadband, High Luminosity B Factory**_**”, giving access to B****d****, B****u****, B****s****, b-baryon, and B****c**** states.**
**Because you are colliding gluons, it is intrinsically asymmetric so time evolution studies are possible (and integrated asymmetries are nonzero)**

**The Challenge**
**The b events are accompanied by a very high rate of background events**
**The b’s are produced over a very large range of momentum and angles**
**Even in the b events of interest, there is a complicated underlying event so one does not have the stringent constraints that one has in an e****+****e****-**** machine**

**These lead to questions about the**
**triggering, tagging, and reconstruction**
**efficiency and the background rejection that can be achieved at a hadron collider**

## Requirements on “The Next Generation”

**Ability to run at high luminosity**
**A very efficient trigger **
**Superb vertex resolution**

**An excellent particle identification **
**A very high speed, high capacity data acquisition  system**
**Excellent photon/********0**** reconstruction **

## Key Design Features of BTeV

-  A dipole located ON the IR,  gives BTeV TWO spectrometers -- one covering  the forward  proton rapidity region and the other covering the forward antiproton rapidity region. _**See following**_
- A precision vertex detector based on planar pixel arrays
- A vertex trigger at Level I which makes BTeV especially efficient for states that have only hadrons. The tracking system  design has to be tied closely to the trigger design to achieve this.
- Strong particle identification based on a Ring Imaging Cerenkov counter. Many states that will be of interest in this phase of B physics will only be separable from other states if this capability exists. It also allows one to use charged kaons for tagging.
**A lead tungstate electromagnetic calorimeter for photon and ********0**** reconstruction**

## New Condition

- The budget situation has worsened since BTeV’s initial Stage 1 approval by Fermilab
- To compensate, the experiment has been rescoped:
- Only one arm will be instrumented, at least initially (sensitivity implications)
- The IR will be constructed from components liberated from the existing collider experiment IRs when one of them concludes (scheduling implications)
- Much of the offline computing hardware will be provided via using university resources made available over the network using grid software and relying on university and funding agency IT resources
- This lowers the cost by about $70M to about a $100M.

## Reduced Scope  BTeV Spectrometer

**Since B’s are**
**produced by gluon-**
**gluon fusion,  both**
**B’s are boosted in**
**the direction of the**
**more energetic gluon,**
**and go into the same**
**arm. If this were not**
**so, tagging would not**
**be efficient with one**
**Arm.**

- Toroid

-  The Re-scoped Version of BTeV ‘s Stage I approval was recently reconfirmed, unanimously, by the FNAL PAC.

## Comparison  to e+e- 

**At Snowmass, the E2 Working Group established that a**
**10****35**** luminosity e****+****e****- ****machine, the end point of upgrades to existing machines,  had 1/10 the events as BTeV for B****d**** and B****u**** physics. BTeV is unrivalled  for B****s ****or other B hadrons.**

**It concluded that for e+e- to be competitive would require a machine capable of a luminosity of 10****36****!! **_**This would not be an upgrade of PEP II but a new machine. **_

**BABAR would have to be completely rebuilt and much R&D**
**would be needed to develop several high risk technologies**

## Comparison of a Single Arm BTeV with LHCb

| Mode | Branching Ratio | BTeV
Yield | BTeV
S/B | LHCb
Yield | LHCb
S/B |
| --- | --- | --- | --- | --- | --- |
| B->+/-  | 2.8x10-5 | 5400 | 4.1 | 2140 | 0.8 |
| Bo->oo | 0.5x10-5 | 776 | 0.3 | 880 “naïve,
No backgnd | <0.05 My
estimate |

- Event Yields and Signal to Background for Bo

- 

**BTeV is  a factor of 2.5 better in raw yield and a factor of 4 when background dilution is accounted for**. **Unclear whether LHCb can even do ****B****o****->********o********o ****due to**** ****poor signal to background**** , ****but again would be a factor of four worse in effective number of events. ****LHCb cannot do ********etc.**
** ****BTeV’s superior trigger, based on the pixel detector,  and DAQ make it more able to follow new paths that may open up as more is learned**

## BTeV Schedule

- BTeV could be built by 2008, with substantial portions in place by 2007.
- BTeV is designed so components can be installed on the fly a little at a time on collider down days.We can run low luminosity, 1030, collisions at the end of stores. We can debug detectors on flux from a wire target in the beam halo when collisions are not available. **We can be commissioned before the final IR is complete. This is worth at least a year, if not more.**
- The character of this physics is that it unfolds gradually as statistics are accumulated over a few years. In the end small differences in the starting time can be overcome by a superior detector. If we did start late w.r.t. LHCb, we have a sufficient advantage in some KEY states that we could rapidly catch up, e.g. 4x better in -.
- We assume that the moment when the transition to BTeV will  be made will be determined by physics considerations with due respect to the laws of statistics.
- Fermilab will begin to think about a “plan B” involving the construction of new magnets for C0, in case the physics of RUN 2 dictates that the two existing detectors continue.

## BTeV R&D Highlights and Plans

- Pixel Detector: achieved design (6-10 micron) resolution in 1999  FNAL test beam run. Demonstrated radiation hardness in exposures at IUCF. Will have a test of almost final readout chip in FNAL testbeam in 2002
- Straw Detector: prototype built, to be tested at FNAL in 2002
- EMCAL: two runs at IHEP/Protvino demonstrated resolution and radiation hardness. More tests in fall to verify stability of calibration system
- RICH: HPD developed and bench tested.  Full test cell under development for beam test at FNAL in 2003
- Muon system tested in 1999 FNAL Test beam run. Better shielding from noise implemented and bench-tested. Desin to be finalized in FNAL test beam in 2002
- Silicon strip electrical and mechanical design well underway
- Trigger code implemented on FPGA, Prototypes being constructed. NSF/RTES proposal approved to write fault tolerant software for massively parallel systems

- Work supported by DOE/FNAL, DOE/University
- Program, NSF, INFN, IHEP, and others.

## Pixel Beam Results

**Solid curve** is the approximation used in BTeV simulations

- Track angle (mr)

- No change
- after 33 Mrad
- (10 years, worst  case, BTeV)

**Analog output of pixel amplifier **
**before and after 33 Mrad irradiation.**
**0.25******** CMOS design verified radiation**
**hard with both ******** and protons. Also**
**measured SEU cross section, which**
**is acceptable**

- More tests will be carried
- out in FNAL test beam in
- the summer/fall

## HPD Schematic

- HPD Tube

- HPD Pixel array

- HPD Pinout

**Pulse Height from**
**163 pixel prototype**
**HPD. Note pedestal,**
**1, 2, 3 pe peaks**

##  Forward Tracker

- Prototype Straw tracker
- being constructed for FNAL
- beam test summer/fall 2002

**Muon Detector**

- Prototype Muon “Plank”
- being tested at Vanderbilt
- in preparation for beam
- test and FNAL

## Lead Tungstate Electromagnetic Calorimeter

- Resolution as measured in
- Test beam at IHEP/Protvino.
- Stochastic term = 1.8%

## BTeV Physics Reach - 1 Year

**Quantity  **                         **Uncertainty (********)**
- 				_**2 x 10**_**32**
**	****	****	****	****1year**
****** ****sin2********	****	****0.018**
****
****************
******	**
******s********D****s****K****	****	****	**** ************o**
**************D****o************************o**
**    ****B****o********************(plus theory)**
**Sin(2********)**
**   ****B****s****->J/********(‘)****                                    0.03**
****** ****asym****	****                        ****	****	****0.034**
**x****s**** ****(D****s********)****	****                        ****	****	****up to 60**

## Concluding Remarks

**BTeV will make critical contributions to our knowledge of CP Violation as attention turns from initial observations to the work of finding out if the Standard Model explanation  is correct and complete.**
**BTeV is  not just doing Standard Model physics. It is sensitive enough to reveal new phenomena.**
**BTeV makes excellent use of an existing DOMESTIC HEP facility in which there has and will have been a huge investment**
**The R&D projects are critical to developing the technologies that will make these experiments possible. The work will insure that they will succeed and will increase the likelihood that they can be done on schedule and on budget.**
**Hopefully, BTeV will form a key part of a world class domestic flavor physics program after the LHC takes firm possession of the energy frontier**