# Presentation: 644186

**Very Long Baseline experiment with a **
**Super Neutrino Beam **
**Brookhaven National Laboratory**
**Presented to the**
**NuFact04, Osaka University**
**Stephen Kahn**
**Brookhaven National Laboratory**
**For the Brookhaven Neutrino Working Group**
**References:**
** ****Phys Rev D 68, 012002 (2003)**
**Talks at BNL-UCLA Neutrino Super Beam Workshop**
**M. Diwan’s talk at APS Super Beam Study Group Meeting**
**B. Viren’s talk at UNO Collaboration Meeting (April ’04)**

- S. Kahn

- July 30, 2004

## Physics Goals of the

**Physics Goals of the**
**Very Long Baseline Neutrino Program**** **

- We introduce a plan to provide the following goals in a ***single facility***:
- 	 precise determination of the oscillation parameters ****m**32****2** and sin**2**2******23**
- 	 detection of the oscillation of ********** ******** ********e** and measurement of sin**2**2******13**
- 	 measurement of ****m**21****2** sin**2**2******12** in a ********** ******** ********e** appearance mode, can be
- 	   made if the value of ******13 **is zero
- 	 verification of matter enhancement and the sign of m**32****2**
- 	 determination of the CP-violation parameter ******CP** in the neutrino sector
- The use of a *single neutrino super beam source* and *half-megaton neutrino*
*detector* will optimize the efficiency and cost-effectiveness of a full program
- of neutrino measurements.  If the value of sin**2**2******13** happens to be larger than
- ~0.01, then all the parameters, including CP-violation can be determined in
- the VLB program presented here.

- S. Kahn

- July 30, 2004

## BNL Homestake  Super Neutrino Beam

**BNL ********Homestake  Super Neutrino Beam**

**2540 km**

- BNL

- 28 GeV protons, 1 MW beam power
- 500 kT Water Cherenkov  detector
- 5×107 sec of running, Conventional Horn based beam

- The baseline design: BNL-Homestake  2540 km
- A potentially better site: BNL-Henderson  2767 km
- If the right detector (LAr) is build there:  BNL-Soudan 1712 km

- S. Kahn

- July 30, 2004

## Flexibility to Handle Tomorrow’s Physics

- At this point we do not know many of the critical parameters that describe the neutrino mixing sector.
- The facility must be flexible to parameter changes so that it is not obsolete before it is built.
- The first phase is a wide-band  beam that should measure 3-generation mixing with CP at some precision.
- 1 MW super beam with 0.5 Mton H2O Č detector (or equivalent)
- Based on future knowledge of the mixing parameters, the running strategy can be adjusted.
- Wide band anti-neutrino running with an upgrade to a 2 MW beam.
- An off-axis  beam with a narrower and lower energy spectrum to suppress background
- The ability to have a 1° off axis beam is being designed into the facility.

- S. Kahn

- July 30, 2004

## AGS Target Power Upgrade to 1 MW

**AGS Target Power Upgrade to 1 MW**

-  the *AGS Upgrade* to provide a source for the 1.0 MW Super Neutrino Beam
-   Existing AGS is in red, Upgrades to the AGS are shown in blue.
- Increase AGS cycle time to 2.5 Hz, add 1.2 GeV Superconducting Linac instead of the booster.

- No new technology is required for the upgrade.

- S. Kahn

- July 30, 2004

## AGS 1 MW Upgrade and SC Linac Parameters

**AGS 1 MW Upgrade and SC Linac Parameters**

**Proton Driver Parameters**
**Item****	****Value**
- Total beam power	1 MW
- Protons per bunch	0.410**13**
- Beam energy	28 GeV
- Injection turns	230
- Average beam current	38 mA
- Repetition rate	2.5 Hz
- Cycle time	400 ms
- Pulse length	0.72 ms
- Number of protons per fill	9.6 10**13**
- Chopping rate	0.75
- Number of bunches per fill	24
- Linac average/peak current	20/30 mA

**Superconducting Linac Parameters**
**    ****Linac Section****	****  LE****	****  ME****	****  HE**
- Av Beam Pwr, kW	7.14	14.0	14.0
- Av Beam Curr, mA	35.7	35.7	35.7
- K.E. Gain, MeV	200	400	400
- Frequency, MHz	805	1610	1610
- Total Length, m	37.82	41.40	38.32
- Accel Grad, MeV/m	10.8	23.5	23.4
- norm rms ****, **** mm-mr	2.0	2.0	2.0

- We would want an eventual upgrade to 2 MW for running.

- This should provide 2.41020 protons per 107 seconds.  (SSC year)

- S. Kahn

- July 30, 2004

## Super Neutrino Beam Geographical Layout

**Super Neutrino Beam Geographical Layout**

-  BNL can provide a *1 MW capable*
*   **Super Neutrino Beam* for $104M
-    FY03 (TEC) dollars
-  the neutrino beam can aim at any
-    site in the western U.S.;  the
-    Homestake Mine is shown here
-  there will be no environmental
-    issues if the beam is produced
-    atop the hill illustrated here and
-    the beam dumped well above
-    the local water table
-  construction of the Super Neutrino
-    Beam is essentially de-coupled
-    from AGS and RHIC operations

- S. Kahn

- July 30, 2004

## 3-D Neutrino Super Beam Perspective

**3-D Neutrino Super Beam Perspective**

- The neutrino will be inclined 11.3° with respect to the surface

- The target building is 50 m above ground level.

- S. Kahn

- July 30, 2004

## Slide 9

- S. Kahn

- July 30, 2004

## Wide Band Neutrino spectrum from AGS

- Proton energy 28 GeV
- 1 MW total power
- ~10** ****14** proton per pulse
- Cycle 2.5 Hz
- Pulse width 2.5 mu-s
- Horn focused beam with graphite target
- 5x10**-5  **/m2/POT @ 1km

- S. Kahn

- July 30, 2004

## Slide 11

- S. Kahn

- July 30, 2004

## Event Rates Seen at the Far Detector

- Non Oscillating event rates seen in a H2O Č detector at the Homestake Lab assuming:
- 1 MW source (2 MW for  running).
- 500 kT fiducial volume
- 5107 sec running period with 1.221022 total 28 GeV protons.
- Backgrounds in the quasi-elastic channel are manageable:
- e beam contamination estimated at ~1% and can be measured.
- NC single 0.  Needs to be demonstrated.

- S. Kahn

- July 30, 2004

##  Disappearance with a Very Long Baseline

- Neutrino oscillations result from the factor sin2(m322L/4E) modulating the  flux.
- The oscillation period is directly proportional to the distance and inversely proportional to the energy.
- With a very long baseline the actual oscillations are seen in the data as a function of E.
- The multiple-node structure allows m322 to be precisely measured by a wavelength rather than an amplitude ratio, reducing systematic errors.

- From the Quasi-elastic channel:

- S. Kahn

- July 30, 2004

## Baseline Length and Neutrino Energy

**Baseline Length and Neutrino Energy**

-  for a fixed phase angle, e.g. ****/2,
-    the ratio of distance to energy is
-    fixed (see sloped lines in Figure)
-  the useful neutrino energy range
-    in a beam derived from a proton
-    production source is restricted:
-      below ~0.5 GeV by *Fermi mom.*
-      in the target nucleus
-      above ~8 GeV by *inelastic *******
*     **interactions* background
-  these conditions prescribe a
-    needed baseline of greater than
-    *2000 km* from source to detector
-  by serendipity, the distance from
-    BNL to the Homestake Mine
-    in Lead, SD is 2540 km

- S. Kahn

- July 30, 2004

## Probability of   e through earth

- Below 1.5 GeV: m221 contribution increases at low energy.
- 1-3 GeV : small matter effect, large CP effect.
- Above 3 GeV matter enhancement by about factor of 2.
- Very long baseline separates physics effects.

- S. Kahn

- July 30, 2004

## Very Long Baseline Application to Measurement of m322

**Very Long Baseline Application to Measurement of ********m****32****2**

- Comparison of the precision of measuring m322 between the following experiments:
-  BNL Very Long Baseline with 5 years running
- Expected Minos results with planned 3 year running period.
- Existing SuperK results.
- Do not expect better precision without a Neutrino Factory.

- S. Kahn

- July 30, 2004

## e Appearance Measurements

-  a direct measurement of the
-    appearance of **************e** is important;
-    the VLB method competes well with
-    any proposed super beam concept
-  for values > 0.01, a measurement
-    of sin**2**2******13** can be made (the
-    current experimental limit is 0.12)
-  for most of the possible range of
-    sin**2**2******13**, a good measurement of
-    ******13** and the CP-violation parameter
-    ******CP** can be made by the VLB
-    experimental method

- S. Kahn

- July 30, 2004

## Backgrounds to e Appearance Signal

- e contamination in the beam coming from Ke3 and  decays.
- This is expected to be ~1%.
- The e contamination will be well measured in the close-in detector.
- NC single 0 events where the 0 decay is sufficiently asymmetric that only one  is seen and it is confused with an electron.
- The peak in the NN0 distribution is independent of E.
- The N0 distribution falls 2 orders of magnitude 2.5 GeV
- The N0 background should be manageable above ~2 GeV.
- We have attempted to evaluate background spectrum from not being able to resolve photons with less than 20° separation.
- Large effect at lower energies
- Some effect on disappearance
- Some effect on appearance with E>2.5 GeV.

- S. Kahn

- July 30, 2004

## Slide 19

- S. Kahn

- July 30, 2004

## CP-violation Parameter 

**CP-violation Parameter **

- S. Kahn

- July 30, 2004

## Slide 21

- S. Kahn

- July 30, 2004

## Possible limits  on sin2213  versus CP 

- Possible limits  on sin**2**2******13 ** versus ******CP**

-  **For normal mass ordering **
**  ****limit on** sin**2**2******13 ****will be 0.005 **
**  ****for no CP**
** ****Any experiment with horn **
** ****focused beam is unlikely to **
** ****do better.**
**  ****If reversed mass ordering **
**  ****then need to run **
**  ****antineutrinos**

- S. Kahn

- July 30, 2004

## Resolution on CP phase

- Resolution gets better rapidly as ****m**21****2 **becomes larger.
- Resolution of 20 deg as long as signal sufficiently above background.

- S. Kahn

- July 30, 2004

## Sensitivity to Sin2213

- Figure shows expected 90% CL limits for sin2213 vs. m31 for various experiments.
- The BNL VLB will produce the best measurement of sin2213 before a Neutrino Factory.

- S. Kahn

- July 30, 2004

## Detector Choices

- The baseline choice for the far detector is H2O Cherenkov similar to UNO.
- This was done merely to permit calculations for our study with known parameters.
- There are cost concerns for a 0.5 megaton detector.  H2O Č tends to be a cost effective approach to large detectors.
- We need software improvements to increase 0 rejection.  (C. Yanagisawa, SUNY-SB)
- Possible focusing photo-detectors to give photon direction information.
- Aqua-Rich type technology.
- Liquid Argon may be promising.
- Very good resolution.
- Very good sensitivity to e,  should reduce NC 0 background.
- May be able to use 100kT because it is not restricted to quasi-elastic events.
- It may not be as expensive as we thought.
- Large Cryo liquid CH4 commercially available.
- Argon is cheap.

- It should be the community that designs the detector, not the laboratory.
- Your input (and work) is appreciated.

- S. Kahn

- July 30, 2004

## The Near Detector

- The close-in detector will be necessary to determine the composition of the beam.
- It will see ~109 events during the running period.
- Structure function physics.
- It will provide a precise measurement of e contamination in the beam.
- It would be desirable to have a magnetic field to separate antineutrinos.
- It would be desirable to have the similar technology as the far detector to cancel systematic effects such as pion reabsorption in the nucleus.
- The close-in detector will be located 285 m from the target.
- The location is dictated be the steep beam incline to reach Homestake.
- The neutrino source will not be a point source.
- This is similar to the situation for the close detector at J-Parc.
- Techniques to determine the far detector flux will have to be developed.

- S. Kahn

- July 30, 2004

## How Much Will This Cost?

**How Much Will This Cost?**

**	****	****AGS Upgrade & SC Linac****	****	****$156.8M****	****(C-AD staff, recent SNS and BNL experience)**
**	****	****Neutrino Beam Cost           ****	****    61.7M****	****(C-AD/Phys. Dept. staff, recent BNL experience)**
**	****	**_**EDIA, Conting., Proj. G&A**__**	**__**	**__**  150.0M  (BNL project experience and current rates)**_
**	****	****Total Estimated Cost (TEC)****	****$368.5M  (fully burdened)**
**	****	****  ****3 yrs R&D ($1M, 3M, 5M)****	****	****      9.0M****	****(estimated *****accelerator***** R&D in FY04, 05, 06)**
**	****	**_**  **__**Pre-ops, starting in FY09**__**	**__**	**__**    12.0M  (this would accomplish the needed pre-ops)**_
_**	**__**	**_**Total Project Cost****	****(TPC)****	****	****$389.5M  (fully burdened)**
**	****	****These estimates are provided in ****FY 2003 dollars**** and are for the *****Accelerator and ***
***	******	******Super Neutrino Beam elements only*****.  ****These costs *****do not *****include the detector.**
**	****	****The basis of estimate comprises current costs that C-AD and BNL engineers **
**	****	****and ****	****physicists derive from recent and ongoing BNL projects.  The level of EDIA is**
**	****	****scaled from recent BNL projects in HENP areas of DOE.**

- These numbers are being revised

- S. Kahn

- July 30, 2004

## When Can We Have It?

**The *****technology***** (not budget) *****limited***** *****schedule***** would comprise:**
** ****a 3-year R&D period (FY04-06)**
**a 5-year construction period (FY07-11)**
**the *****critical path***** would definitely be the R&D:**
** ****to develop the *****superconducting RF cavities***
**To develop the ***** RF power system*****.   **
**All the other systems would require less R&D time. **
**There are *****no novel or unproven technologies***** in the accelerator and neutrino beam concept.**

- S. Kahn

- July 30, 2004

## Conclusions

**Conclusions**

- 	 measurement of the *complete set of neutrino mass and mixing *
*	**   **parameters* is very compelling for the advance of particle physics
- 	 the *Very Long Baseline* method, utilizing a *1 MW Super Neutrino Beam*
- 	   from BNL’s AGS, coupled with a *half-megaton water Cerenkov detector*
- 	   in the Homestake Mine in Lead, SD, offers a uniquely effective plan
- 	 the half-megaton detector was not detailed in this presentation but
- 	   we note that the UNO detector has all the properties needed for the VLB
- 	   neutrino program and offers important and compelling physics beyond
- 	   the neutrino oscillations work.
- 	neutrino only running,  low sensitivity to systematics,
-   high sensitivity to mass ordering, broad spectrum of physics.
-   We can decide at a later point to run anti-neutrinos to increase precision.
- 	This plan received high marks from HEPAP facilities committee in February.

- S. Kahn

- July 30, 2004

## Backup Slides

- There is no time to show these slides unless specific questions are asked.
- 1 degree off axis beam
- Breaking 23 Degeneracy
- Liquid Ar at 1770 km

## Slide 31

- S. Kahn

- July 30, 2004

## Slide 32

- S. Kahn

- July 30, 2004

## Slide 33

- S. Kahn

- July 30, 2004

## Slide 34

- S. Kahn

- July 30, 2004

## Slide 35

- S. Kahn

- July 30, 2004

## With a Liquid Argon Detector at 1770 km

- S. Kahn

- July 30, 2004

## e Appearance Measurements if no CP Violation

******e**** Appearance Measurements if *****no***** *****CP Violation***

-  even if sin**2**2******13** = 0, the current
-    best-fit value of ****m**21****2 **= 7.3x10**-5**
-    induces a ******e** appearance signal
-  the size of the ******e** appearance signal
-    above background depends on the
-    value of ****m**21****2**; the figure left
-    indicates the range of possible
-    measured values for the ******e**
-    yields above background for various
-    assumptions of the final value of
-    ****m**21****2**

- S. Kahn

- July 30, 2004