# Presentation: 561620

## Options for E906/Drell-Yan with a Solid Iron Magnet(Fe906?)Paul E. Reimer20 June 2008

*Solid Iron magnet *
*Target dump separation*
*Chamber rates*
*Resolution—Mass, x**F**, x**1**, x**2*
*Acceptance*

## Why a Solid Iron Magnet?

- E906 budget is very tight.
- We are expecting ≈$2M for DOE/Nuclear Physics.  Of this $1.6M will be used to produce coils for an open aperture magnet.  The remainder is for spectrometer upgrades.
- NSF, Taiwan and Japan are planning contributions to the spectrometer upgrades
- Fermilab has requested that we contribute an additional $1.5M for M&S that they need to spend for E906
- Some tasks e.g. flammable gas system (Illinois) and cryotargets may be done by collaborators.
- RIKEN may to contribute ≈$600k to “common fund” items
- Still short ≈$500k

- Solid Iron Magnet
- Essentially free—coils and iron exist, Iron must be cut ($100k)
- Reprogram DOE/ONP funds to Fermilab  (Under discussion with Brad Tippens)
- Increased acceptance--larger “aperture” (if you can call it that)
- Decreased resolution

- Paul E. Reimer

- 20 June 2008

## Magnet Description 

- Use existing coils from SM3
- 3 coil packs:
*191, 163 or 135 inch coils*
- Iron blocks from SM12 (E866) magnet
- Simulations shown for 191”
**Suggested by Chuck Brown**

- 135”

- 191”

- SM3 coils which were constructed in 1981 for E605 by Sumitomo and supervised by KEK and Kyoto. Supervised by Prof. Miyake, Dr. Maki and Dr. Sakai

- Paul E. Reimer

- 20 June 2008

## Magnet Description

- Use existing coils from SM3
- 3 coil packs
- 191, 163 or 135 inch coils
- Simulations shown for 189”
- Issues:
- Target/dump separation
- Chamber rates
- Mass Resolution
- x2 resolution
- Field simulation
*no measurements*
*Accurately determine saturation curve*
- Acceptance (i.e. statistical uncertainty at the end of the day)

- Field simulation for 189” solid Fe magnet (DFG)

- Paul E. Reimer

- 20 June 2008

## Dump/Target Separation

***Dump/Target Separation***

- Resolution significantly worse
- Trigger and reconstruction  cuts allow for clean separation
- Remove events with tracks at dump face within 2.25” of beam axis
- Remove events with tracks greater than 10” from beam axis at targets
**Recall dump starts at 0”.  These cuts effectively remove all events from the front of the dump!!**

- Target

- Open aperture in red
- Solid Fe in Blue

- Dump

- Dump

- Target

- Slight problem from dump J/’s

- Paul E. Reimer

- 20 June 2008

## Dump/Target Sep., Solid Fe Magnet Only

***Dump/Target Sep., Solid Fe Magnet Only***

- Target—solid histograms
- -70 < z < -50
- Dump—dashed histo.
- 0<z
- Magenta, all events
- Green: Magneta and
- xF>0 and
- M>4.5 GeV
- and pz>20 GeV
- Blue: Green and
- |ytrack|>2.25 in at z=0 (dump face)
- Red:  Blue and
- |ytrack|<10.0 in at z=-60 (target)

- Reconstructed

- Generated

- Paul E. Reimer

- 20 June 2008

## Station 1 Chamber Rates

***Station 1 Chamber Rates***

- Occasionally a muon showers in the absorber
- If this happens in the center of the absorber, no effect is seen as shower is also absorbed
- If this happens in the last few inches of the absorber, shower can create extremely large rates in Station 1 (of low momentum particles)
- Solution is to have an absorber-free region at the end of the field volume and use field as a sweeper
- In Solid Iron magnet, there is no absorber-free sweeper region! (Can we find a wide gap sweeper magnet?)
**Requires GEANT MC to see magnitude of effect**

- Absorber and B Field

- Sta. 1

- 

- Absorber and B Field

- Absorber and B Field

- B Field only

- Paul E. Reimer

- 20 June 2008

## Mass Resolution

***Mass Resolution***

- Reconstruction of Muon tracks yields virtual photon properties:
- M2, xF, pT
- Mass resolution dictates J/ cut
- Critical for x2 (and x1) resolution

- Drell-Yan

- J/
- 450 MeV
- (and don’t forget about the 0)

- Drell-Yan

- J/
- 470 MeV
- (and don’t forget about the 0)

- “Standard” E906 Analysis Mass cut of 4.5 GeV

- Paul E. Reimer

- 20 June 2008

## Mass Calibration

***Mass Calibration***

- Track reconstruction apparently skews virtual photon mass
- Events with tracks which significantly miss target have poor mass reconstruction

- yrtp and yrtn are the reconstructed y offsets of the two tracks at a plane perpendicular to the beam in the center of the target.  P and n denote positive and negative.
- Mass is the difference between generate and reconstructed mass in the Monte Carlo

- Drell-Yan (M>4.5 GeV) MC in black
- J/ MC in red

- Use known mass (J/) to calibrate this correction
- Effect is slightly different, but similar to higher mass Drell-Yan

- Paul E. Reimer

- 20 June 2008

## Calibrated mass resolution

***Calibrated mass resolution***

- Introduces mass offset in Drell-Yan mass range (4.5 < M<8.5 GeV) but better than uncorrected

- Drell-Yan

- J/
- 298 MeV

- Significant improvement near J/
- General improvement at all masses

- Paul E. Reimer

- 20 June 2008

## xF Resolution

- No Known xF point to use for calibration.

- Paul E. Reimer

- 20 June 2008

## x1 Resolution

***x******1****** Resolution***

- x1 resolution ***worse*** with correction

- Resolution for all x1

- Resolution x1≥ 0.75

- Paul E. Reimer

- 20 June 2008

## x2 Resolution

***x******2****** Resolution***

- x2 resolution improved by correction.
- Resolution significantly worse for high x2—is this a problem?

- Resolution for all x2

- Resolution x2≥ 0.35

- Recall D-Y falls exponentially with x2.
- Events may be reconstructed into neighboring bins.

- Paul E. Reimer

- 20 June 2008

## x2 resolution—solid iron and miss reconstruction

***x******2****** resolution—solid iron and miss reconstruction***

**Can we live with this misidentification? Or find an additional correction**

- Red events have reconstructed to the correct x2 bin
- For a significant fraction of the events, x2true is
- one (blue) or
- two (green)
- bins lower than x2recon.

- Essentially no data in this bin

- Paul E. Reimer

- 20 June 2008

## x2 resolution— Open Aperture and miss reconstruction

***x******2****** resolution— ******Open Aperture****** and miss reconstruction***

- Red events have reconstructed to the correct x2 bin
- Open aperture design also suffered from misreconstruction, but not as much as solid iron design

- Essentially no data in these bins

- Does anyone want to look at this in E866 data?

- Paul E. Reimer

- 20 June 2008

## Statistical Precision

- Increased statistical precision w/Solid Fe Magnet
- Larger transverse “aperture” in Solid Fe Magnet (34” vs. 25”)
- Larger Station 3 wire chamber
- Needed to take advantage of larger aperture
- Note: open aperture would also benefit from larger station 3
- Part of Japanese contribution

**Significant gain in large-x****2**** region**
- Open Ap. Design may also gain in Stat. as well from larger Station 2 & 3 combination

- Paul E. Reimer

- 20 June 2008

## Drell-Yan Ratio Statistical Uncertainty

- Better Statistical Uncertainty at high x2
- Crude trigger matrix applied
- not used in previous plots
- Accounts for fall-off at low x2 in solid iron magnet

- Paul E. Reimer

- 20 June 2008

## 126 inch Magnet

- Resolution in Mass and x2 not better
- Lower acceptance at high-x2
- See relative normalization

- Mass

- All x2

- x2 for x2 > 0.35

- Paul E. Reimer

- 20 June 2008

## Magnet Polarity:which events do we want?

- We really want the high-x2 events
- All the other events come for free

- Paul E. Reimer

- 20 June 2008

## Magnet polarity 8 GeV

- Paul E. Reimer

- 20 June 2008

## Magnet Polarity 6 GeV

- Paul E. Reimer

- 20 June 2008

## Magent Polarity 4 GeV

- Paul E. Reimer

- 20 June 2008

## Magnet Polarity 3 GeV

***Conclusion***

- Running in opposite polarity **may** allow smaller chambers
- Important for Station 3 which is LARGE
- Acceptance must be verified with Monte Carlo
- Preliminary Monte Carlo shows resolution is the same (expected)

- Paul E. Reimer

- 20 June 2008

## Things left to do

- Independent verification of results
- Background rate simulations
- See GEANT MC talk—this seems to be in hand
- Opposite Polarity MC with reduced Sta. 3 size
- I’ve run the MC and could have results next week
- Resolution improvements with target retrace?
- Angular resolution for cos 2 distributions
- Partonic Energy Loss—is x1 resolution good enough?
- What is the saturation curve of the SM12 iron—this clearly effects the field
- Some data from Chuck *et al.* that must be analyzed

- Paul E. Reimer

- 20 June 2008

## Resolution is poorer with Solid iron magnet, but acceptable?
x2 bin resolution
Dump/Target separation is achievable

- Resolution is poorer with Solid iron magnet, but acceptable?
- x2 bin resolution
- Dump/Target separation is achievable

***Conclusion:  Solid Fe magnet will work ***(always listen to Chuck)

- Essentially no data in this bin

- Larger aperture provides better statistical precision at high x2
- Opposite polarity configuration may allow for smaller Station 3 and 4 chambers

- Paul E. Reimer

- 20 June 2008