Electro-weak Precision Tests with nuSTORM Sanjib Kumar Agarwalla - - PowerPoint PPT Presentation
Electro-weak Precision Tests with nuSTORM Sanjib Kumar Agarwalla Sanjib.Agarwalla@ific.uv.es IFIC/CSIC, University of Valencia, Spain S. K. Agarwalla, nuSTORM Workshop, Fermilab, USA, 22 nd September, 2012 Electro-weak Theory The
Sanjib Kumar Agarwalla Sanjib.Agarwalla@ific.uv.es
IFIC/CSIC, University of Valencia, Spain
The Standard Model (SM) provides a remarkably accurate description
The SM unifies the weak and electromagnetic forces into one gauge group, SU(2)L × U(1)Y Weak sector è precision at 0.1% level are reached Electromagnetic sector è precision at 1 part per billion The SM is incomplete due to è Ø the discovery of neutrino mass Ø the existence of dark matter Ø the recent advent of dark energy
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Precision low energy observables have been and continue to be an invaluable tool to learn about the scale of new physics and to shed light into flavor sector These tests are complimentary to the more canonical measurements done at colliders like LHC looking for new physics at higher energy scales These tests are highly sensitive to the presence of oblique corrections affecting vacuum polarization of the photon, Z and W bosons through new particles in quantum loops and vertex corrections
M.E. Peskin and T. Takeuchi, Phys. Rev. Lett. 65, 964 (1990)
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The Weinberg angle is defined by the ratio of the SU(2)L gauge coupling g and the U(1)Y gauge coupling g′ è a key parameter in the electro-weak theory Its value depends on the energy scale. Renormalization group running of the Weinberg angle is an inevitable consequence
Experimental demonstration of the running of the Weinberg angle has been considered to be an experimentum crucis for the SM
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S.K. Agarwalla and P. Huber, JHEP 1108 (2011) 059
World data for the Weinberg angle as a function of Q Solid curve shows the running in the MS-bar renormalization scheme
W
2
SLAC E158 PVDIS [JLab] Qweak [JLab] Moller [JLab] Future Existing SM
b FB
A [LEP]
LR
A [SLD] dis
(MS)
APV(Cs)
100 10 1 0.1 0.01
Q (GeV)
0.001 0.25 0.245 0.24 0.235 0.23 1000
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Leptonic (0.23113 ± 0.00021) and hadronic (0.23222 ± 0.00027) measurements of sin2θW at Z-pole differ by 3.2 standard deviations NuTeV collaboration reported a 3σ discrepancy with the SM value
These discrepancies could be a sign for new physics or may be for not understood experimental effects
The ALEPH, DELPHI, L3, OPAL, SLD Collaborations, Phys. Rept. 427, 257 (2006) G.P. Zeller etal., [NuTeV Collaboration], Phys. Rev. Lett. 88, 091802 (2002) [Erratum-ibid. 90, 239902 (2003)] 5/15
sin2θW .vs. Higgs mass
¤ SM prediction for sin2θW as a function of Higgs mass ¤ Precise information on sin2θW is very helpful to constrain the Higgs mass
10 2 10 3 0.23 0.232 0.234
sin2
lept eff
mH [GeV]
2/d.o.f.: 11.8 / 5
A
0,l fb
0.23099 ± 0.00053 Al(P) 0.23159 ± 0.00041 Al(SLD) 0.23098 ± 0.00026 A
0,b fb
0.23221 ± 0.00029 A
0,c fb
0.23220 ± 0.00081 Q
had fb
0.2324 ± 0.0012 Average 0.23153 ± 0.00016
had= 0.02758 ± 0.00035 (5) mt= 178.0 ± 4.3 GeV
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¤ Eµ = 3.8 GeV with 1.8 × 1018 effective µ+ decays in 5 years ¤ Length of the Straight Section = 150 m ¤ Distance between the front end of the storage ring and detector = 20 m / 50 m / 100 m ¤ 1 kt LArTPC (Radius = 2.8 m & Length = 22.57 m) with 100% efficiency ¤ Energy resolution, σ(E) in GeV = 5% × √E in GeV ¤ 50 MeV bin-size in reconstructed recoil kinetic energy
L = 20 m / 50 m / 100 m dx
x
dl
Radius = 2.8 m 1 kt LAr detector Storage Ring
25 m Arc
Straight section = 150 m Detector depth = 22.57 m
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20 m, 1 kt 50 m, 1 kt 100 m, 1 kt 20 m, 60 tons 50 m, 60 tons 100 m, 60 tons
Work in progress with Christopher Tunnell
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Simple, purely leptonic, weak interactions, plays an essential role to prove the validity and perform precision tests of the SM
Eν = Incoming neutrino energy, T = Electron recoil kinetic energy θ = Angle between incident neutrino direction and recoil electron The values of α and β in the SM for different processes
The signal is a forward electron track with no hadronic activity The transverse momentum of the outgoing electron is very small,
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Work in progress with Christopher Tunnell
[10 m ]
2 electron neutrino e scattering CCQE
0.5 1 1.5 2 2.5 3 3.5 4 E [GeV] 1000 10 1 0.1 100
Main source of background in studying the ν-e scattering process is quasi-elastic νeN scattering But, the transverse momentum of the outgoing electron is very large for CCQE process compared to ν-e scattering CCQE : ν-e scattering : We can use the pt and Ee cut to
reject most of the CCQE
backgrounds provided that the
detector has very good angular
and energy resolution!
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Work in progress with Christopher Tunnell
Looking for electron neutrino Deep-inelastic backgrounds rejected looking at the hadronic activity Further cuts like: Ep > 50 MeV and θp > 20 degrees
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Work in progress with Christopher Tunnell
¤ What type of electron energy resolution can we expect? ¤ What type of angular resolution can we expect for LAr? ¤ HIRESMNU has 0.2 degrees for 2 GeV electrons ¤ Intrinsic angular resolution limited to 1 degree from accelerator
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Work in progress with Christopher Tunnell
nue & numubar convoluted Muon energy = 3.8 GeV Distribution of signal events
w/o cut
100 m, 1 kt 50 m, 1 kt 20 m, 1 kt
1 1.5 2 2.5 3 3.5 4
Reconstructed Electron energy [GeV] Events per 50 MeV Bin
600 500 400 300 200 100 0.5 w/ cut
100 m, 1 kt 50 m, 1 kt 20 m, 1 kt
500 600 0.2 0.4 0.6 0.8 1 1.2 1.4
Reconstructed Electron energy [GeV] Events per 50 MeV Bin
300 200 100 400
To reject CCQE background, we consider an energy window of 0.05 GeV to 1.5 GeV in reconstructed recoil electron kinetic energy and an angular cut of cosθ > 0.9961946
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Work in progress with Christopher Tunnell Total neutrino electron scattering event rates in 1 kt detector Relative error on weak mixing angle at 1σ We consider an energy window of 0.05 GeV to 1.5 GeV in reconstructed recoil electron kinetic energy and an angular cut of cosθ > 0.9961946
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2
W PVDIS [JLab] Qweak [JLab] Moller [JLab]
LR
(MS)
A [SLD]
b FB
A [LEP] dis
Existing SM nuSTORM APV(Cs) SLAC E158
0.01 0.001 0.25 0.24 100 0.23 0.225 Q (GeV) 0.235 1000 10 0.245 1 0.1
Work in progress with Christopher Tunnell
Preliminary
nuSTORM will provide a ≈ 1.5% measurement
Q ≈ 2 GeV More studies on electro-weak measurements will come soon! Thank you!
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