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Beta Beam based on machine upgrades for the LHC. Luca Scotto Lavina Università ”Federico II” and INFN, Napoli, Italy. A. Donini, E. Fernandez Martinez, P. Migliozzi, S. Rigolin, L. S. L., T. Tabarelli de Fatis, F. Terranova, hep-ph/0604229 . Otranto, Italy, 15/09/2006. Motivations.

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slide1

Beta Beam based

on machine upgrades for the LHC

Luca Scotto Lavina

Università ”Federico II” and INFN, Napoli, Italy

A. Donini, E. Fernandez Martinez, P. Migliozzi, S. Rigolin, L. S. L.,

T. Tabarelli de Fatis, F. Terranova,

hep-ph/0604229

Otranto, Italy, 15/09/2006

slide2

Motivations

  • Is there a window of opportunity for neutrino oscillation physics compatible with the machine upgrades of the LHC (>2015)?
  • Can we immagine an affordable facility that could fully exploit european infrastructures during the LHC era?
  • Is the sensitivity adequate for an experiment aiming at closure of the PMNS (precision measurement of the 1-3 sector)?

Luca Scotto Lavina NOW 2006 15/09/2006

slide3

Sensitivity plot

vs time for Phase I experiments

hep-ph/0606111

1.7° @ 2015

Phase I

Phase II

2022

2009

2012

2014

Beam upgrade and

HK construction

T2K - Nona

Data taking...

q13 discovery ?

2022

2007

2012

2015

“Phase 2” lumi upgrade of the LHC

LHC Energy upgrade?

LHC and Double CHOOZ startup

End of CNGS

slide4

How to approach Phase II in Europe?

  • Many ideas have been put on the market
    • Different accelerator technologies
    • Different baselines
    • Different detector technologies
  • We think that Phase II in Europe should be part of a common effort of the Elementary Particle community
    • Exploit as much as possible technologies common to other fields (e.g. LHC upgrades, EURISOL)
    • Exploit already existing infrastucture (e.g. LNGS halls)
    • Costs reduction!

Luca Scotto Lavina NOW 2006 15/09/2006

slide5

Multi-MW SuperBeam

  • Technology similar to conventional n beams 
  • Neutrino beam has contamination from other flavours 
    • Main source of systematics
  • Proton driver to be built from scratch 
    • Useful for Neutrino Factory
  • Low energy neutrino beams 
    • Huge low density detectors mandatory (i.e. water Č)
  • Underground laboratory to be built from scratch

(e.g. SPL-Frejus) 

    • Gran Sasso halls are too small to host Mton detectors

Luca Scotto Lavina NOW 2006 15/09/2006

slide6

Neutrino Factory

  • Excellent neutrino beam 
    • Flux composition very well known
  • Very challenging technology 
    • Start operations > 2020 (not suitable in a short term period)
  • No relevant overlap with CERN accelerators 
  • Possible the study of the “silver channel” (νe→ν) 
  • If built at CERN, Gran Sasso Lab maybe too close 

Luca Scotto Lavina NOW 2006 15/09/2006

slide7

Beta Beam

  • Excellent neutrino beam 
    • Flux composition very well known
  • Possibility to work in νμ appearance mode
    • νμ CC are an easier channel than ne CC and allows for dense detector
  • No need to distinguish νμ from anti-νμ
    • No need for magnetic detectors!
  • Many energy configurations are envisaged:
    • g ~ 150 (current design),
    • g ~ 350 (S-SPS based design),
    • g > 1000 (LHC based design)

Luca Scotto Lavina NOW 2006 15/09/2006

slide8

Comparison of the different designs

  • Current design (EURISOL DS)
    • Strong synergy with present CERN accelerator complex 
    • Low energy beam: needs huge and low density detectors 
    • Underground lab to be built from scratch (e.g. Frejus) 
    • Counting experiment 
    • Excellent θ13 and δ sensitivity 
    • No sensitivity to neutrino hierarchy 
  • S-SPS
    • Strong synergy with a LHC energy/luminosity upgrade 
    • Medium energy beam: small and high density detectors start to be effective 
    • Underground lab already exists (e.g. Gran Sasso) 
    • Spectrum analysis possible 
    • Very good θ13 and δ sensitivity (slightly smaller than current desing) 
    • Sensitivity to neutrino hierarchy 
  • NB both designs need an ion decay ring!

Luca Scotto Lavina NOW 2006 15/09/2006

slide9

The Beta Beam complex

. . . + a decay ring

Not needed for a Beta Beam

Present design

lenght: 6880m

useful decays: 36%

5 T magnets

S-SPS based design

lenght: 6880m

useful decays: 23%

8.3 T magnets (LHC)

Luca Scotto Lavina NOW 2006 15/09/2006

slide10

ν

Why S-SPS is so interesting?

  • It is able to bring 6He up to g≤350 (18Ne up to g ≤580)
    • Neutrino energy above 1 GeV (spectrum analysis)
  • It is not in contrast with the LHC running

ν

ν

  • Iron detectorsare already effective
  • Fermi motion is no more dominant (energy reconstruction)
  • Baseline fits the CERN-LNGS distance (730 km) and is large enough to study neutrino hierarchy
slide11

The detector at the Gran Sasso

See e.g. T.Tabarelli @ LCWS05

Expected unoscillated e CC

events per kton-year

  • 40 ktoniron (4 cm thickness) and glass RPC
  • Digital readout (2x2 cm2 pads)
  • No magnetic field
  • Full GEANT3 simulation but event selection based on inclusive variables only (n. hits, layers etc.)  can be improved with pattern recognition
slide12

Event classification

Neutrinos with  = 350

Antineutrinos with  = 350

Luca Scotto Lavina NOW 2006 15/09/2006

slide13

Signal efficiency

and background mis-identification

as a function of the neutrino energy

Neutrino

Antineutrino

Luca Scotto Lavina NOW 2006 15/09/2006

slide14

Assumptions

  • Oscillation parametersinput taken from: G.L. Fogli, E. Lisi, A. Marrone, A. Palazzo, hep-ph/0506083
  • Three flavour analysis, but only the intrinsic degeneracy (δ-θ13 correlation) is taken into account: sign(Δm223) = +1, θ23 = 45°
  • We assumed for neutrinos  = 350,580 and antineutrinos  = 350
  • We assumed 10 years run
  • We assumed thenominal beta-beam fluxes (F0) assumed also for  = 100. Not a bad assumption given the γ-duty factor impact on the fluxes, the S-SPS intensityx2
  • We assumed a 2% systematic error on the cross-sections.
    • Realistic assumptions. Minerva, T2K-near will measure μ cross-section in our region of interest with an accuracy better than 2%
    • There is no need of a “conventional” -beam to measure the μ cross-section (e.g. SPL to Frejus)

Luca Scotto Lavina NOW 2006 15/09/2006

slide15

Expected number of events

after 10 years exposure

Luca Scotto Lavina NOW 2006 15/09/2006

slide16

The analysis

Multi-bin likelihood (bin=0.25 GeV of reconstructed energy)

180

0

-180

0

0

15

15

4

7

13 (deg)

13 (deg)

Luca Scotto Lavina NOW 2006 15/09/2006

slide17

Discovery potential vs Flux

Minimum 13 can be discovered,

assuming  = 90°

Minimum  can be discovered,

assuming 13 = 3°

Black curves:  (18Ne)=350 ,  (6He)=350, 10y with “nominal” flux (F0), 99% C.L.

Red curves:  (18Ne)=580 ,  (6He)=350, 10y with “nominal” flux (F0), 99% C.L.

slide18

 discovery potential

F0/2

F0

F0x2

For comparison: SPS-based Beta Beam with Mton-size water Cherenkov detector

Left curves:  (18Ne)=350 ,  (6He)=350, 10y run, 99% C.L.

Right curves:  (18Ne)=580 ,  (6He)=350, 10y run, 99% C.L.

F0 is the

“nominal” flux

slide19

13 exclusion plot

F0/10

F0/2

F0

F0x2

Left curves:  (18Ne)=350 ,  (6He)=350, 10y run, 90% C.L.

Right curves:  (18Ne)=580 ,  (6He)=350, 10y run, 90% C.L.

F0 is the

“nominal” flux

slide20

Neutrino hierarchy

Matter effects perturb

the transition probabilities

Sign of m223

can be distinguished

A simultaneous fit of the energy distributions for  and -bar allows to improve the measurement of the neutrino hierarchy

We assume the normal hierarchy as the true one.

If we assume the inverted hierarchy as the true one, the plot is almost symmetric

Black curve:  (18Ne)=350 ,  (6He)=350, 10y with “nominal” flux (F0), 99% C.L.

Red curve:  (18Ne)=580 ,  (6He)=350, 10y with “nominal” flux (F0), 99% C.L.

slide21

Neutrino hierarchy

Normal hierarchy

Inverted hierarchy

Luca Scotto Lavina NOW 2006 15/09/2006

slide22

Conclusions

  • The Super-SPS option for the luminosity/energy upgrade of the LHC strenghten enormously the physics case of a Beta Beam in Europe
    • No need of ultra-massive (1Mton) detectors
    • Possibility to leverage existing underground facilities (Gran Sasso laboratories)
    • Full reconstruction of the event in nm appearance mode
    • Baseline appropriate for exploitation of matter effects
  • If Phase I experiments discover θ13, the proposed BB will be able to measure δCP≠0° down to 30° for θ13≥3° and to measure the sign of Δm223 down to 2° (δCP=+90°)

We strongly support a more detailed study

of this scenario

Luca Scotto Lavina NOW 2006 15/09/2006

slide23

S-SPS technology

(accidentally) ideal for high-energy BB

  • It provides a fast ramp (dB/dt=1.21.5 T/s) allowing for a reduction of the ion decays during the acceleration phase
  • Super-SPS more performant than SPS (x2 intensity, faster cycle)
  • Fluxes could be smaller than Frejus (higher g means higher lifetime)
    • High field magnets (11-15 T) in the decay ring would increase the number of useful decays (higher flux) OPTIONAL!
  • We can allocate more ion bunches in the decay ring because we do not need a <10ns bunch length to get rid of the atmospheric background  
    • We can recover the losses due to the higher g (… see next slide)

Luca Scotto Lavina NOW 2006 15/09/2006

slide24

ν

The duty cycle issue

  • In order to reduce theatmospheric backgroundthe timing of the parent ion is needed:
  • Strong constraint on the number of circulating bunches and on the bunch length

In the present design:

  • bunch length 10 ns (very challenging) (10-3 suppression factor)
  • 8 circulating bunches

Frejus

S-SPS

With the S-SPS based scenario the atmospheric background is reduced by about a factor 10 and the bunch length can be correspondently increased

ν

ν