Accelerator-based neutrinos Lecture 1
Kendall Mahn
26/08/2015, INSS K.Mahn, Acc-nu sources 1 Neutrino sources The Sun (fusion) Galac c and Our atmosphere extra-galac c sources (e.g SN)
Radioac ve Accelerators decays
Reactors
26/08/2015, INSS K.Mahn, Acc-nu sources 2 Neutrino sources The Sun (fusion) Galac c and Our atmosphere extra-galac c sources (e.g SN)
At solar neutrino energies, mean free path through lead is 1 light year
Making precision neutrino measurements require enormous detectors and intense sources
Radioac ve Accelerator-driven neutrino beams are one such method Accelerators decays
Reactors
26/08/2015, INSS K.Mahn, Acc-nu sources 3 Physics of accelerator based ν experiments
Neutrino oscilla on • Measurements of neutrino mixing parameters • Nonstandard neutrino mixing
Electroweak tests • Lorentz viola on 2 • Measurement of sin θW • Discovery of νµ, ντ
Neutrino interac ons • Charged current interac ons • Neutral current interac ons • Deep inelas c sca ering • Structure func ons
Detector R&D
26/08/2015, INSS K.Mahn, Acc-nu sources 4 Physics of accelerator based ν experiments
Neutrino oscilla on K2K, MINOS, T2K, NOvA • Measurements of neutrino mixing parameters OPERA (& ICARUS) • Nonstandard neutrino mixing LSND, Karmen, MiniBooNE, MicroBooNE CHORUS, NOMAD Electroweak tests • Lorentz viola on CCFR, CDHS, NuTeV 2 • Measurement of sin θW Gargamelle, DONUT • Discovery of νµ, ντ CHARM
Neutrino interac ons • Charged current interac ons ANL, BNL bubble chamber • Neutral current interac ons experiments • Deep inelas c sca ering SciBooNE, MINERvA • Structure func ons COHERENT, CONNIE
Detector R&D
Incomplete list of experiments; later lectures will ArgoNeuT cover future and proposed experiments PEANUT Most experiments cover mul ple physics topics
26/08/2015, INSS K.Mahn, Acc-nu sources 5 Physics of accelerator based ν experiments
Neutrino oscilla on K2K, MINOS, T2K, NOvA • Measurements of neutrino mixing parameters OPERA (& ICARUS) • Nonstandard neutrino mixing LSND, Karmen, MiniBooNE, MicroBooNE Focus for this set of talks CHORUS, NOMAD Electroweak tests • Lorentz viola on CCFR, CDHS, NuTeV 2 • Measurement of sin θW Gargamelle, DONUT • Discovery of νµ, ντ CHARM
Neutrino interac ons Neutrino cross sec ons covered by K. McFarland • Charged current interac ons ANL, BNL bubble chamber • Neutral current interac ons experiments • Deep inelas c sca ering SciBooNE, MINERvA • Structure func ons COHERENT, CONNIE
Detector R&D Neutrino detec on techniques covered by K. Scholberg ArgoNeuT PEANUT
26/08/2015, INSS K.Mahn, Acc-nu sources 6 Open ques ons about neutrino mixing Open questions in neutrino mixing
# νe & #Ue1 Ue2 Ue3 & # ν1 & Flavor eigenstates % ( % ( % ( Mass eigenstates (coupling to the W) νµ = Uµ1 Uµ2 Uµ 3 ν2 (definite mass) % ( % ( % ( $ ντ ' $Uτ1 Uτ 2 Uτ 3 ' $ν3 ' Unitary PMNS mixing matrix
Three observed flavors of neutrinos (νe, νµ , ντ) means U is represented by three independent mixing angles (θ , θ , θ ) and a CP-viola ng phase δ 12 23 13 Measurements by accelerator-based experiments
Is θ23 mixing maximal (θ23=46°±3°)
Is there CP viola on (non- PDG2014 PDG2014 zero δ?)
26/08/2015, INSS K.Mahn, Acc-nu sources 7 Open ques ons about neutrino mixing Open questions in neutrino mixing
3
2 Δm 32 > 0 2 2 2 Δmij = mi − m j 2 2 Δm 21 1
2 Neutrino mass squared (m€ i ) Neutrino oscilla on measurements are sensi ve to the interference of the mass eigenstates (Δm2)
Two observed mass “spli ngs”, determined from atmospheric/accelerator and solar/reactor neutrino experiments, respec vely 2 2 -3 2 § Δm (atmospheric) = |Δm 32|~ 2.4 x 10 eV 2 2 -5 2 § Δm (solar) = Δm 21 ~ 7.6 x 10 eV
26/08/2015, INSS K.Mahn, Acc-nu sources 8 Open ques ons about neutrino mixing Open questions in neutrino mixing
3 2 2 Δm 21 2 Δm 32 > 0 1
m2 2 Δ 32 < 0 2 Δm 21 1 3
2 Neutrino mass squared (mi )
2 The sign of Δm 32, or the “mass hierarchy” is s ll unknown 2 § Normal “hierarchy” is like quarks (m1 is lightest, Δm 32 >0 ) 2 § Inverted hierarchy has m3 lightest (Δm 32 <0)
What is the mass hierarchy?
26/08/2015, INSS K.Mahn, Acc-nu sources 9 Oscilla on probabili es Oscillation probabilities
2 2 |Δm 32| >> Δm 21, producing high frequency and low frequency oscilla on terms
( 1.27Δm2 L + ( 2.54Δm2 L+ P 4 Re U U * U * U sin2 ij 2 Im U U * U * U sin ij αβ = δαβ − ∑ [ βi αi βj αj ] * - + ∑ [ βi αi βj αj ] * - i> j ) E , i> j ) E ,
2 2 2 If choose L, E, such that sin (Δm 32L/E) is of order 1, then Δm 21 terms will be € small. Then... ν “disappear’’ into ν , ν µ e τ ( 1.27 m2 L + 2 2 Δ 32 P(νµ → ν µ ) ≅ 1− sin 2θ23 sin * - ) E ,
A small amount of νe will “appear’’ 2 2 Δm 31 ~ Δm 32 € 2 2 2 2 ' 1.27Δm31L * P(νµ → νe ) ≅ sin 2θ13 sin θ23 sin ) , ( E + Only leading order terms shown
26/08/2015, INSS K.Mahn, Acc-nu sources 10 € Accelerator-basedAccelerator based neutrino neutrino sources sources
95m Decay region Neutrino beam π+
30 GeV Carbon 3 Magne c Pions and kaons Beam Proton beam Target focusing decay to neutrinos dump ``horns”
To measure νµ disappearance, and νe appearance requires a νµ source* § Atmospheric neutrinos include both νe and νµ from produc on § Accelerator based beams are pure νµ from a proton -> meson -> decay chain: § Typically >99.9% νµ § Produc on of neutrinos is “known”, scalable with accelerator improvements § Also possible to create an neutrino source
*There are other ways to probe oscilla on physics with intense sources, more later
26/08/2015, INSS K.Mahn, Acc-nu sources 11 Oscilla on probabili es Oscillation probabilities
νµ to νe appearance probability expansion:
E A =2 2G N F e m2 32
Key players: 2 -3 2 § |Δm 32|~ 2.4 x 10 eV (atmospheric mass spli ng) § Mixing angles: θ12, θ23, θ13 Approxima on from § CP-viola ng phase δCP M. Freund, PRD 64, 053003
Neutrinos vs. an neutrinos probability depends on δCP, mass hierarchy (sign 2 of Δm 32 ) • Mass hierarchy is determined through energy dependence of νe, νµ interac ons in ma er (ma er effects, A terms) 26/08/2015, INSS K.Mahn, Acc-nu sources 12 Oscilla on probabili es Oscillation probabilities
νµ to νe appearance probability expansion:
E A =2 2G N F e m2 32
Key players: 2 -3 2 § |Δm 32|~ 2.4 x 10 eV (atmospheric mass spli ng) § Mixing angles: θ12, θ23, θ13 Approxima on from § CP-viola ng phase Subleading terms of δCPνµ to νe appearance depend on δCP, mass hierarchy, but interpreta on requires precision measurements of: M. Freund, PRD 64, 053003 Δm2 , θ (disappearance) and Δm2 , θ and θ Neutrinos vs. an neutrinos probability depends on 32 23 21 δ12CP, mass hierarchy13 (sign 2 of Δm 32 ) Measurements of νµ to νe (and νµ to νe ) appearance are sensi ve to • Mass hierarchy is determined through energy dependence of currently unknown physics νe, νµ interac ons in ma er (ma er effects, A terms) 26/08/2015, INSS K.Mahn, Acc-nu sources 13 Oscillation probabilities
2 2 2 ( 1.27Δm32 L + P(νµ → ν µ ) ≅ 1− sin 2θ23 sin * - ) E ,
2 2 Measure: Δm 32 and sin 2θ23 Experimental controls: § Fix beam energy (E) € § Place a detector at L, the (first) oscilla on maximum
Why not place two detectors, one at L and one at 2L? P(ν ) µ Flux decreases as 1/L2:
Osc maximum Event rate scales with flux: N = Φ x σ x ε P(ν ) ξ Event rate is (currently) too small
26/08/2015, INSS K.Mahn, Acc-nu sources KARMEN website graphic 14 Long baseline experiments
2 2 2 ( 1.27Δm32 L + P(νµ → ν µ ) ≅ 1− sin 2θ23 sin * - +... ) E ,
Unknown road to Unknown road - Google Maps http://maps.google.com/maps?hl=en&tab=wl Δm2 ~3x10-3 eV2, want sin2(Δm2 L/E) to be of order 1 32 To see all the details that are visible on the screen, use the "Print" link next to the map. Tokai To € Kamioka (T2K) experiment: MINOS experiment: Eν(peak) ~0. 6GeV, L=295km Eν(peak) ~3 GeV, L=735km
First part of lecture: What are the physics results from long baseline experiments?
©2011 Google - Imagery ©2011 TerraMetrics -
26/08/2015, INSS K.Mahn, Acc-nu sources 15
1 of 1 4/23/11 10:27 AM Accelerator-basedThe Tokai-to- Kamiokaexperiment experiment example: T2K
The physics so far:
νµ to νe (and νµ to νe) appearance: § Discovery of νe appearance (2013) § Search for presence of appearance Neutrino flux at SK with an neutrinos; necessary step (no oscilla on) toward future CPV searches
νµ, νµ disappearance: § World’s best measurement of θ23 § With an neutrinos: test of NSI or CPT theorem
26/08/2015, INSS K.Mahn, Acc-nu sources 16 νµ disappearance at T2K
For a fixed baseline (L=295km) 2 2 2 ( 1.27Δm32 L + oscilla on probabili es depend on P(νµ → ν µ ) ≅ 1− sin 2θ23 sin * - +... ) E , the neutrino energy Eν
2 2 Data Extract Δm , sin θ23 from observed 60 change in overall rate and spectrum MC€ Unoscillated Spectrum 40 MC Best Fit Spectrum § Energy es mated using lepton
NC MC Prediction
Events/0.10 GeV momentum, angle and assumed 20 CCQE kinematcs
0 0 2 4 > 5 PRD 91, 072010 (2015) Reconstructed ν Energy (GeV) 10
1
10−1
10−2 0 2 4 > 5
Osc. to unosc Events/0.1 GeV Reconstructed ν Energy (GeV)
26/08/2015, INSS K.Mahn, Acc-nu sources 17 T2K observed event distributions) 4 /c 2 T2K data favors maximal disappearance 3.2 eV -3 § Provides best constraint on θ to date, SK joint OA
23 (10 3 consistent with maximal (45°) mixing 2 32 m ∆ 2.8 T2K joint OA
2.6
2.4
2.2 MINOS joint OA
0.3 0.35 0.4 0.45 0.5 0.55 0.6 0.65 0.7 ) 4 -2 /c 2 eV -3 -2.2 MINOS joint OA (10 2 32 PRD 91, 072010 (2015) m -2.4 ∆
-2.6
-2.8 T2K joint OA
-3 SK joint OA
0.3 0.35 0.4 0.45 0.5 0.55 0.6 0.65 0.7 2 sin θ23 26/08/2015, INSS 18 K.Mahn, Acc-nu sources T2K observed event distributions) 4 /c 2 T2K data favors maximal disappearance 3.2 eV -3 § Provides best constraint on θ to date, SK joint OA
23 (10 3 consistent with maximal (45°) mixing 2 32 m ∆ § Atmospheric measurements also 2.8 T2K joint OA important (SK, IceCube) 2.6 Best constraint on mass spli ng from MINOS experiment 2.4 • Energy uses lepton and hadronic state 2.2 MINOS joint OA
0.3 0.35 0.4 0.45 0.5 0.55 0.6 0.65 0.7 ) 4 -2 /c 2 eV -3 -2.2 MINOS joint OA (10 2 32 PRD 91, 072010 (2015) m -2.4 ∆
-2.6
-2.8 T2K joint OA
-3 SK joint OA Phys. Rev. D 85, 031103(R) (2012) 0.3 0.35 0.4 0.45 0.5 0.55 0.6 0.65 0.7 Phys. Rev. Le . 101, 131802 (2008) 2 sin θ23 26/08/2015, INSS 19 Phys.Rev.D71:112005 (2005) K.Mahn, Acc-nu sources T2K observed event distributions
New! NOvA first results § Compelling measurement with only 7.6% of total data expected § Consistent with T2K and MINOS + atmospheric measurements
M. Sanchez, NuFact2015 26/08/2015, INSS 20 K.Mahn, Acc-nu sources T2K observed event distributions New! T2K first an neutrino disappearance results § Probe of NSI; consistent with neutrino measurement
34 events seen, 34 expected
26/08/2015, INSS 21 K.Mahn, Acc-nu sources Oscilla on probabili es νe appearance
νµ to νe appearance probability depends on all other mixing parameters
PRD 91, 072010 (2015)
Understanding δCP currently requires informa on about θ23 (and mass hierarchy)
Cri cal input from reactor measurements of θ13 26/08/2015, INSS K.Mahn, Acc-nu sources 22 Oscilla on probabili es νe appearance
νµ to νe appearance probability depends on all other mixing parameters
NOnA 1s and 2s Countours for Starred Point NOnA NOnA Nominal Run 810km Baseline 3.6E21 PoT n + n 2 sin 2q13=0.09 0.08 2 § Ellipse maps out how sin 2q23=1.00 A. Norman H L δCP changes the Neutrino 2014 oscilla on probability Inverted § Comparisons between 0.06 Ê neutrino/an neutrino
L · e
appearance oscilla on n Æ m
probabili es will be used n Á H to infer δ , mass P 0.04 Ê CP ‡ Á hierarchy 2s · 1s ¯‡ 0.02 Normal
Á d=0 Ê d=p 2 · d=p ‡ d=3p 2 0.00 0.00 0.02 0.04 0.06 0.08 ê
P nmÆne ê 26/08/2015, INSS K.Mahn, Acc-nu sources 23 H L Oscilla on probabili es νe appearance
νµ to νe appearance probability depends on all other mixing parameters
NOnA 1s and 2s Countours for Starred Point NOnA NOnA Nominal Run 810km Baseline 3.6E21 PoT n + n 2 0.08 sin 2q13=0.09 sin22q =0.95 § Ellipse maps out how 23 A. Norman H L δCP changes the Neutrino 2014 oscilla on probability Ê § Comparisons between 0.06 · Á neutrino/an neutrino Inverted L e appearance oscilla on n ‡Ê
Æ Ê m n
probabili es will be used H Á 2s
P 0.04 · to infer θ23 octant · 1s Á Ê ¯‡ Á ‡ · 0.02 ‡ Normal Á d=0 Ê d=p 2 · d=p ‡ d=3p 2 0.00 0.00 0.02 0.04 0.06 0.08ê
P nmÆne ê
26/08/2015, INSS K.Mahn, Acc-nu sources 24 H L T2K νe appearance
2 Fit to νe candidates’ rate and 2 2 2 ' 1.27Δm31L * kinema c distribu ons to P(νµ → νe ) ≅ sin 2θ13 sin θ23 sin ) , ( E + determine oscilla on parameters
Signal # events Signal: CC νe candidates 2 @sin 2θ13=0.1,δcp=0 €21.06 from νµ to νe oscilla on 2 -3 2 2 νε signal@Δm 32 =2.4 x 10 eV , sin 2θ23=1.0 For T2K neutrino data set Tag νe by selec ng electron-like rings Background # events (proton below threshold)
beam νe + νe 3.54 CCπ CCQE νe
νµ + νµ (mainly NC) 1.43 ν e ν background total: 4.97 W W n p π N Δ N’
26/08/2015, INSS K.Mahn, Acc-nu sources 25 T2K νe appearance
2 Fit to νe candidates’ rate and 2 2 2 ' 1.27Δm31L * kinema c distribu ons to P(νµ → νe ) ≅ sin 2θ13 sin θ23 sin ) , ( E + determine oscilla on parameters
Signal # events Signal: CC νe candidates 2 @sin 2θ13=0.1,δcp=0 €21.06 from νµ to νe oscilla on 2 -3 2 2 νε signal@Δm 32 =2.4 x 10 eV , sin 2θ23=1.0 For T2K neutrino data set Tag νe by selec ng electron-like rings Background # events (proton below threshold)
beam νe + νe 3.54 CCπ CCQE νe
νµ + νµ (mainly NC) 1.43 ν e ν background total: 4.97 W W Data event: n p π N Δ single electron N’
26/08/2015, INSS K.Mahn, Acc-nu sources 26 T2K νe appearance
2 Fit to νe candidates’ rate and 2 2 2 ' 1.27Δm31L * kinema c distribu ons to P(νµ → νe ) ≅ sin 2θ13 sin θ23 sin ) , ( E + determine oscilla on parameters
Signal # events Background: CC νe candidates 2 @sin 2θ13=0.1,δcp=0 €21.06 Irreducible νe produced in beam 2 -3 2 2 νε signal@Δm 32 =2.4 x 10 eV , sin 2θ23=1.0 For T2K neutrino data set Iden cal to signal except for Eν dependence Background # events
beam νe + νe 3.54
νµ + νµ (mainly NC) 1.43 background total: 4.97
26/08/2015, INSS K.Mahn, Acc-nu sources 27 T2K νe appearance
2 Fit to νe candidates’ rate and 2 2 2 ' 1.27Δm31L * kinema c distribu ons to P(νµ → νe ) ≅ sin 2θ13 sin θ23 sin ) , ( E + determine oscilla on parameters
Signal # events Background: NC with a π0 2 0 @sin 2θ13=0.1,δcp=0 €21.06 π decay to two photons; single photon 2 -3 2 2 νε signal@Δm 32 =2.4 =2.4 x 10x 10 eV , sin 2θ23=1.0 mimics CC νe (electromagne c shower) in For T2K neutrino data set Cherenkov detector
Background # events NCπ0 beam ν + ν 3.54 e e ν ν
νµ + νµ (mainly NC) 1.43 background Z
total: 4.97 N π Δ N’
26/08/2015, INSS K.Mahn, Acc-nu sources 28 T2K νe appearance
2 Fit to νe candidates’ rate and 2 2 2 ' 1.27Δm31L * kinema c distribu ons to P(νµ → νe ) ≅ sin 2θ13 sin θ23 sin ) , ( E + determine oscilla on parameters
Signal # events Background: NC with a π0 2 0 @sin 2θ13=0.1,δcp=0 €21.06 π decay to two photons; single photon 2 -3 2 2 νε signal@Δm 32 =2.4 =2.4 x 10x 10 eV , sin 2θ23=1.0 mimics CC νe (electromagne c shower) in For T2K neutrino data set Cherenkov detector
Background # events NCπ0 beam ν + ν 3.54 e e ν ν
νµ + νµ (mainly NC) 1.43 background Z
total: 4.97 N π MC event: Δ π0 N’
26/08/2015, INSS K.Mahn, Acc-nu sources 29 T2K νe appearance results
Data 28 candidate events observed 8 Best fit νe Background component § First observa on of CC νe appearance! 6 Fit region < 1250 MeV § Phys. Rev. Le . 112, 061802 (2014)
4 candidate events
e Signal # events ! 2 2 @sin 2θ13=0.1,δcp=0 21.06
0 0 500 1000 1500> 2000
Number of Reconstructed neutrino energy (MeV) Background # events
beam νe + νe 3.54
νµ + νµ (mainly NC) 1.43 background total: 4.97
26/08/2015, INSS K.Mahn, Acc-nu sources 30 Antineutrino appearance analysis T2K antineutrino appearance results
Normal hierarchy Inverted hierarchy Expect 3.73 (4.18) events based on β scales green normal (inverted) hierarchy
Test of no νe appearance hypothesis: • Significant expected contribu on from νe appearance
• β=0: no νe appearance • β=1: νe appearance
7/24/2015 K. Mahn, FNAL W&C seminar 31 Rate only p-value and sensitivity T2K antineutrino appearance results
Generate an ensemble of test experiments with β=0 (no νe appearance) § p-value: frac on of test experiments that have as many or more candidate events as T2K data § Sensi vity: mean p-value for an ensemble of fake data experiments with β=1
Rate p-value Likelihood only ra o Data: 0.26 0.9 3 events
Likelihood ra o: L(β=0)/L(β=1) is close to 1
Data does not favor or disfavor νe appearance
7/24/2015 K. Mahn, FNAL W&C seminar 32
3 2 Rate+shape distribution of candidate events T2K antineutrino appearance results
Signal only Background only ( = 0) 2 ln = 2lnLmarg L ( = 1) Lmarg
Data does not favor or disfavor νe appearance
7/24/2015 K. Mahn, FNAL W&C seminar 33
3 3 NOvA νe appearance results
M. Sanchez, NuFact2015
6, 11 candidate νe events observed with two selec ons in tracking detector § Also signal dominated (~1 event background) § 3.3σ/5.5σ evidence for
CC νe appearance § Consistent with T2K
26/08/2015, INSS K.Mahn, Acc-nu sources 34 NOvA νe appearance results
Electromagne c shower of one candidate M. Sanchez, NuFact2015
6, 11 candidate νe events observed with two selec ons § Also signal dominated (~1 event background) § 3.3σ/5.5σ evidence for
CC νe appearance § Consistent with T2K
26/08/2015, INSS K.Mahn, Acc-nu sources 35 Aside 1: blind analyses
In a blind analysis, the analysers: § Perform all checks and cross checks required prior to looking at the data; prevents tuning away or enhancing signals § Report any changes post-unblinding § Example: Expect nue appearance. Hide the expected nue appearance signal in a ‘box’ un l the en re analysis chain is prepared and reviewed. Then, count the number of nue candidates § Possible bias: § Revisi ng event selec on a er seeing the data § Could try to reject events (because you want no signal events) or add events to the sample (because you want a signal, this one’s close enough!)
Blindness is to avoid bias, addi onal resources in backups
NOvA used this for their first results
26/08/2015, INSS K.Mahn, Acc-nu sources 36 Aside 2: trials factor
NOvA sees 6 events with one selec on, and 11 events with another selec on § ``Beware of trials factor for choosing 11 events a er the fact’’
Trials factor: With large data sets, expect some number of anomalies (sta s cally) • Example: 200 medical researchers test 200 drugs. One researcher finds a sta s cally significant effect at the 99.9% C.L., and publishes. The other 199 find nothing, and publish nothing. • But, chance of one drug giving a false signal: 0.1%. • Chance that at least one of 199 drugs will give a significant result at this level: 18%
NOvA chose the primary analysis in advance of seeing the event rate, so avoided the risk of choosing the more exci ng answer a er the fact
Report what you measure!
26/08/2015, INSS K.Mahn, Acc-nu sources 37 Global picture of νe appearance
Long baseline experiments depend on δCP + θ13 + … Reactor experiments are pure measurements of θ13 Large number of events observed by T2K, NOvA restrict allowed hierarchy + δCP 1
0.5 ⇥ / 0 CP ⇤
-0.5
PRD 91, 072010 (2015) -1 0.02 0.04 0.06 0.08 0.1 2 sin ( 13)
T2K+Reactor 68% Credible Region T2K Only 68% Credible Region T2K+Reactor 90% Credible Region T2K Only 90% Credible Region T2K+Reactor Best Fit Point T2K Only Best Fit Line
26/08/2015, INSS K.Mahn, Acc-nu sources 38
2 2 α = Δm 12/Δm 32 ~ 0.04 2 2 Δm 31 ~ Δm 32 Global picture of νe appearance
§ T2K, NOvA favors δCP around 3π/2 at 90%CL, disfavored by MINOS? § But hierarchy is not determined due to entanglement with δCP and octant § Not strong statements yet!
PRD 91, 072010 (2015)
2 2 Probability Δm 32>0 Δm 32<0 Sum
2 sin θ23 ≤ 0.5 16.5% 20.0% 36.5%
2 > 0.5 sin θ23 28.8% 34.7% 63.5% Sum 45.3% 54.7% 26/08/2015, INSS K.Mahn, Acc-nu sources 39
2 2 α = Δm 12/Δm 32 ~ 0.04 2 2 Δm 31 ~ Δm 32 Future νe appearance results
T2K collab, arXiv:1409.7469, accepted by PTEP
NOνA’s higher energy (peak Eν~2 GeV) and longer baseline (L~810km) has a different dependence on mass hierarchy through the ma er effect than T2K’s § Gray regions are where the mass hierarchy can be determined to 90% CL for T2K(red), NOνA (blue), and T2K+NOνA (black) for full run of both experiments rd § 95%CL determina on for 1/3 of δCP space for maximal θ23 Unknown complica ons of θ23 and δCP in this equa on mean 26/08/2015, INSS mul ple experiments are K.Mahn, Acc-nu sources complementary 40 The OPERA experiment
On-axis beam (Eν≈17 GeV) CERN to Gran Sasso, Italy (730km)
OPERA physics run: Operated from 2008-2012 Neutrinos: 1.8x1020 POT
Measurements of:
ντ appearance
OPERA plots from S. Dusini, Neutrino2014
26/08/2015, INSS K.Mahn, Acc-nu sources 41 OPERA ντ appearance results
Emulsion film + lead form “bricks” § Scin llator planes and magne c spectrometer are used to iden fy likely neutrino interac on bricks § Bricks removed and scanned to determine τ decay candidate interac ons § precise vertex informa on ντ appearance expected signal 2.10±0.4, background 0.23±0.04 Observed 4 candidate events (no oscilla on excluded at 4.2σ)
26/08/2015, INSS K.Mahn, Acc-nu sources 42 A third appearance experiment
LSND Experiment: observa on of 3.8σ excess of νe in νµ beam “Short baseline”: Eν ~30 MeV, L~30m νe detected with inverse beta decay and delayed n capture 2 2 2 2 There are two independent Δm , as Δm 21 + Δm 32= Δm 31 2 2 2 -5 2 2 -3 2 LSND observed Δm ~ 1eV >> Δm21 (10 eV ) + Δm 32 (10 eV ) Inconsistent with just three mass eigenstates, is it new physics?
26/08/2015, INSS K.Mahn, Acc-nu sources 43 A third appearance experiment
LSND Experiment: observa on of 3.8σ excess of νe in νµ beam “Short baseline”: Eν ~30 MeV, L~30m νe detected with inverse beta decay and delayed n capture 2 2 2 2 There are two independent Δm , as Δm 21 + Δm 32= Δm 31 2 2 2 -5 2 2 -3 2 LSND observed Δm ~ 1eV >> Δm21 (10 eV ) + Δm 32 (10 eV ) Inconsistent with just three mass eigenstates, is it new physics?
Second part of lecture: What are the physics results from short baseline (sterile neutrino) experiments?
26/08/2015, INSS K.Mahn, Acc-nu sources 44 Sterile neutrinos One explana on for the LSND oscilla on signal is to add another “sterile” flavor of neutrino (or 2 or N) to the mixing matrix: Adding 1 sterile neutrino is 3+1, adding N is 3+N
$ νe ' $ν1 ' $U U " U ' &ν ) e1 e2 eN & ) µ & ) ν2 & ) Uµ1 Uµ2 " UµN & ) Uαi = & ντ ) & ) &ν3 ) &Uτ1 Uτ1 " UµN ) &! ) &! ) & ) %& ! ! # ! () & ) %& ν () &ν ) s % N ( 3+1 oscilla on probability: 2 2 2 2 % 1.27Δm41L( P(νµ → νe ) = 4 |Ue4 | |Uµ 4 | sin ' * & E )
2 W.C. Louis, 2 2 2 & 1.27Δm41L) P(νµ → ν x ) = 1− 4 |Uµ 4 | (1− |Uµ4 | )sin ( + Nature, Volume: 478, ' E * Pages: 328–329 €
€ 26/08/2015, INSS K.Mahn, Acc-nu sources 45 The Booster Neutrino Experiments (BooNEs)
• MiniBooNE placed for maximal LSND oscilla on 2 (541 m at 1 GeV; Δm ~ 1eV2) • Different signal iden fica on, systema cs • SciBooNE reused from earlier experiments Beamline now to be used for short baseline neutrino program (SBN)
MiniBooNE target decay SciBooNE 541m Booster horn volume 100m
26/08/2015, INSS K.Mahn, Acc-nu sources 46 MiniBooNE νe appearance analysis
Signal (Dm2=1eV2, sin22q=0.004) Background 0 § misidentified νµ (mainly π s) + § νe from µ decay + 0 § νe from K , K decay § Δ ⇒ Νγ § External backgrounds
Similar to T2K appearance analysis:
• Backgrounds from NC, intrinsic νe
Main difference: much smaller oscilla on probability (0.25%), background dominated
26/08/2015, INSS K.Mahn, Acc-nu sources 47 € • • of Lack
Events/MeV Events/MeV
0.0 0.5 1.0 1.5 2.0 2.5 0.2 0.4 0.6 0.8 1.0 1.2 26/08/2015, INSS ...... 1.6 1.4 1.2 1.0 0.8 0.6 0.4 0.2 Photon background? background? Photon to signal 3+1 mapped not well neutrinos, in tension drives excess energy Low ν µ
→ ν e appearance but observation of but observation appearance MiniBooNE ν MiniBooNE Neutrino Antineutrino MicroBooNE Constr. Syst.Error other dirt Data (staterr.) 0 e e e