10 - SHIP Collaboration

SHIP: un esperimento di
beam dump al CERN-SPS per
la ricerca di HIdden Particles
Walter M. Bonivento
CERN/INFN Cagliari
!
a rappresentare la Collaborazione SHIP
(il sottoscritto e Giovanni De Lellis tra i proponenti)
SPC EOI-2013-010
CNS2 INFN 18/02/2014
Motivazione scientifica
LHC: scoperta Higgs e niente altro finora in ricerche dirette. Idem
nella Fisica del (charged) Flavor. !
Massa del Higgs misurata a ≈125 GeV —> SM teoria di campo
effettiva, auto-consistente, debolmente accoppiata fino a grandi
scale (almeno fino a 1010GeV, vedi Strumia, Giudice, Isidori ecc.)!
Tuttavia rimangono sul tavolo almeno 3 “problemi” sperimentali
dello SM (+altri teorici):!
•
massa dei neutrini!
•
asimmetria barioni-antibarioni universo (BAU)!
•
materia oscura
Walter M. Bonivento - CERN/INFN Cagliari
!2
CNS2 18/02/2014
Su una simile linea di pensiero…
Michelangelo Mangano, Aspen 2014
Walter M. Bonivento - CERN/INFN Cagliari
!3
CNS2 18/02/2014
2
Theoretical motivation
In type-I seesaw models (for a review see Ref. [17]) the extension of the SM fermion sector by three
right-handed (Majorana) leptons, NI , where I = (1, 2, 3), makes the leptonic sector similar to the
quark sector (see Fig. 1). Irrespective of their masses, these neutral leptons can explain the flavour
oscillations of the active neutrinos. Four di↵erent domains of HNL mass, MN , are usually considered:
Possibile soluzione: νMSM
T.Asaka e M.Shaposhnikov, PLB620 (2005) 17
Three Generations
of Matter (Fermions) spin ½
105.7 MeV
0.511 MeV
80.4 GeV
0
Higgs
boson
Right
0
Right
Left
b
bottom
νe N1 νμ N2 ντ N3
~GeV
0
~GeV
0
tau
neutrino
muon
neutrino
electron
neutrino
spin 0
Left
Left
strange
Left
0
-⅓
105.7 MeV
0.511 MeV
γ
0
4.2 GeV
s
~10 keV
0
weak
force
down
gluon
1.777 GeV
photon
91.2 GeV
0
0
Z
0
0
weak
force
80.4 GeV
126 GeV
H
Higgs
boson
spin 0
=
+
, , ;
, , ( , , )
2
mixing
con
neutriniisattivi
where are
the lepton
doublets,
the Higgs doublet, and
couplings
Walter M. Bonivento - CERN/INFN Cagliari
!4
Discovery of Higgs vital for the see-saw model!
tau
Right
muon
Left
-1
Right
electron
Left
weak
force
-1
-1
Right
±
Left
tau
±1
Leptons
τ
Right
Left
muon
-1
Right
electron
Left
e
-1
Right
Left
Leptons
μ
τ
e
W
W
N2 e N3 quasi degeneri massa circa GeV
->oggetto diFigure
questa
proposta;
spiegano la
1: Particle
content of the SM and its minimal extension in the neutrino sector. In the (left) SM the
partners of neutrinos (attraverso
are absent. In the (right) ⌫MSM all fermions have both left- and right-handed
asimmetria right-handed
materia-antimateria
Introduce three
neutraland
fermion
singlets
– right-handed
Majorana leptons
with Majorana
components
masses below
the Fermi
scale.
la leptogenesi
con sphalerons)
e danno
mass
”Heavy Neutral Leptons (HNL)”
Minkowski 1977
massa
ai
neutrini
tramite
il
meccanismo
Yanagida 1979
• Make the leptonic sector similar to the quark sector
Gell-Mann, Ramond, Slansky 1979
see-saw (type 1)!
Glashow 1979
-1
μ
1.777 GeV
0
126 GeV
-⅓
Left
Left
Left
tau
neutrino
muon
neutrino
electron
neutrino
•
0
Left
0
0
0
d
top
Bosons (Forces) spin 1
mixing con gli altri
νμ
ντ
νe due—>candidato
ZDarkH
Matter (ne parlo dopo…piatto caldo!)!
91.2 GeV
charm
0
Left
photon
Bosons (Forces) spin 1
bottom
-⅓
t
g
0
173.2 GeV
⅔
104 MeV
4.8 MeV
Left
Quarks
0
Right
strange
Left
-⅓
Right
Left
down
0
4.2 GeV
-⅓
-⅓
Right
Quarks
γ
s
b
d
N1 di massa circa keV con un piccolo
104 MeV
up
Right
name→
c
⅔
Right
gluon
Left
top
u
III
1.27 GeV
2.4 MeV
charge→ ⅔
0
Right
charm
Right
Right
up
4.8 MeV
Left
•
Left
name→
⅔
Left
⅔
charge→ ⅔
II
I
mass→
0
173.2 GeV
Left
1.27 GeV
2.4 MeV
Left
mass→
Right
soluzione elegante dei
tre IIproblemi
suddetti
III
I
con estensione dello SM: 3 partner di Majorana
g
c
t
u
(HNL) destrorsi e sterili dei neutrini ordinari!
Right
Three Generations
of Matter (Fermions) spin ½
±1
±
weak
force
+ .
are the corresponding new Yukawa
CNS2 18/02/2014
Responsible for the Yukawa couplings!
1.
See-saw: Lower limit on mixing angle with active neutrinos to produce os
2.
BAU: Upper limit on mixing angle to guarantee out-of-equilibrium oscillati
3.
BBN: Decays of
Produzione di N2,3
and
Limit on lifetime
•
•
,
< 0.
must respect current abundances of light nuc
( >3
)
4.
Experimental:
No observation so far
nel2 νMSM forti limitazioni nello spazio
dei parametri
Constraints 1-3 now indicate that previous searches were largely outside interesting
(U ,m)!
molte ricerche di HNL in passato ma, per m>mK, con
sensibilità’ non di interesse cosmologico
(es LHCb in
2
-4
decadimenti del B raggiunge U ≈10 , arXiv:1401.5361)
oduction in mixing with active neutrino from leptonic/semi-leptonic weak decays of
arm mesons
• production
questadepend
proposta:
Total
on
= ricerca in decadimenti dei mesoni D
,
, ,
(prodotti ad alta statistica nella collisione di p di 400
GeV su bersaglio
fisso)!
Relation between
,
and
depends on exact flavour mixing
• il
con i neutrini
attiviassume
e’ dato
da UlI=YlI
For
themixing
sake of determining
a search strategy,
scenario
with a predominant coupling to the muon flavour (arXiv:0705.1729)
Production in mixing with active neutrino from leptonic/semi-leptonic weak de
charm mesons
!
!
!
v/√2 m!
•
Total production depend on
,
, ,
,
,
Future Hadron Collider meeting, CERN, February 6, 2014
•
• la relazione tra Ue, Uμ ecc
oduction
mechanism “probes”
=
mescolamento
tra sapori
Relation between
,
and
depends on exact flavour mixing
dipende dal
For the sake of determining a search strategy, assume scenario
) ~ 10
10
(arXiv:0705.1729)
withCagliari
a predominant coupling to the muon flavour CNS2
Walter M. Bonivento - CERN/INFN
18/02/2014
,
Br(
=
!5
Decadimenti del N2,3
•
Accoppiamento HNL-ν attivo molto debole
—>N2,3 hanno vita media molto lunga
•
distanze di decadimento O(km)!
•
Vari modi di decadimento : i BR’s
dipendono dal mescolamento tra sapori
•
Probabilita’ che N2,3 decada nel volume
fiduciale dell’esperimento
—> numero di eventi
∝U
2
μ
∝
4
Uμ
Walter M. Bonivento - CERN/INFN Cagliari
!6
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Vincoli di progetto
massimizzare l’intensita’ di protoni su bersaglio —>produzione di charm!
•
massimizzare l’accettanza longitudinale!
•
GLi HNL prodotti nel decadimento del charm possono avere un pT significativo e pure i
prodotti di decadimento!
fraction of HNLs/(4 mrad)
!
!
!
!
0.06
angolo polare del
0.05
0.04
0.03
0.02
0.01
0
0
!
•
0.07
fraction of muons/(8 mrad)
•
0.08
0.07
angolo polare del μ
0.06
0.05
0.04
0.03
0.02
0.01
0.05
0.1
0.15
0
0
0.2
0.1
0.2
0.3
0.4
! (rad)
! (rad)
•
il rivelatore deve essere posto il piu’ vicino possibile al bersaglio per massimizzare
l’accettanza
•
la distanza deve essere bilanciata dalla necessita’ di ridurre il flusso di muoni
Sopprimere il fondo di νe e νμ —>bersaglio denso (W vs Cu fa un fattore 2!)
Walter M. Bonivento - CERN/INFN Cagliari
!7
CNS2 18/02/2014
Struttura esperimento: dump
!
wall / earth
!
!
target
hadron
absorber
beam
Experiment
(detector, fiducial volume)
mop−up shielding
muon shield (U / W)
!
!
•
~ 0.5m
•
~ 1m
~ 52m
~ 1m
19
Figure 7: Schematic view of the target, hadron absorber and muon shield in front of the experiment. The total
Fascio SPS estratto
400GeV;
intensità’ come CNGS 4.5x10 pot/anno. Se upgrade PS si
length from
the target to the entrance of the fiducial volume is ⇠ 60 m.
19
puo’ arrivare a 7x10 : caratteristiche dei fasci discusse in grande dettaglio
con esperti del
20
CERN —>design realistico —>5 anni di run SENZA UPGRADE: 2x10 pot!
4.2
•
~ 3m
Detector
detector consists di
of a muoni:
long decay volume
a spectrometer. For a given
length,
Bersaglio di W eTheassorbitore
40m followed
di W, bycomplementato
da detector
Fe o Pb
fino a 60m, o
the detector diameter should be maximised. In the discussion below the 5 m aperture of the LHCb
magneti di sweeping
seguiti da assorbitore in Fe!
spectrometer [59] is taken as a realistic scale.
Figure 8 shows a scan of the length of the detector for both a single detector element and for
9
13
• problema non
twobanale
longitudinally
arrangedil detector
For ae’
given
HNL lifetime
and detector
aperture, the
perche’
flussoelements.
di muoni
enorme:
5×10
/SPS-spill(5×10
pot); 3
5
of HNLs decaying in the apparatus with the decay products going through the spectrometer
possibilita’ dinumber
estrazione
considerate: 1sec, 1msec (riduzione >10 ), 10μs
saturates as a function of the length of the detector. The use of two magnetic spectrometers increases
the geometric acceptance by 70% compared to a single element. Therefore, the proposed detector
sicuramente il problema
tecnico
piu’
difficile
will have two almost
identical
detector
elementsdell’esperimento
as depicted in Fig. 9. A diagram of a single detector
element is also shown in Fig. 10.
To reduce to a negligible level the background caused by interactions of neutrinos with the remaining
air inside the decay volume, a pressure of less than ⇠ 10 2 mbar will be required (see Section 5). Each
Walter M. Bonivento
- CERN/INFN Cagliari
CNS2 18/02/2014
detector element therefore consists of a ⇠50 m long!8cylindrical vacuum vessel of 5 m diameter. The first
⇠ 40 m constitute the decay volume and the subsequent 10 m are used for the magnetic spectrometer.
Tunnel di decadimento e
spettrometro
Vuoto 10-5atm (NB: NA62 10-8atm!)
!
!
L’uso del secondo tunnel aumenta l’accettanza del 70%
Walter M. Bonivento - CERN/INFN Cagliari
!9
CNS2 18/02/2014
Possibile zona sperimentale
Rivelatore
posto IN
SUPERFICIE
Estrazione in SPS-LSS2, beam splitting/switch all’inizio della SPS-NA transfer line (TT20):
gli studi effettuati per il proposal della facility del neutrino molto utili per noi
Walter M. Bonivento - CERN/INFN Cagliari
!10
CNS2 18/02/2014
Rivelatori proposti
•
Quasi nessun R&D da fare: ce la possiamo fare con rivelatori di tipo
tradizionale, ottimizzando i parametri!
•
—>questo significa che dall’approvazione si puo’ iniziare subito a
costruire il rivelatore!
•
Calorimetri EM (x2) : Shashlik tipo LHCb
•
Camere a mu e filtri (x3)—> da progettare. Si potrebbe recuperare da OPERA,
almeno parzialmente.!
•
Camere di tracciamento e di veto (x2): straw tubes come per NA62, bassa X0 ,
0.5% per 4 stazioni!
•
Rivelatore per ντ (vedi dopo)
•
trigger e acquisizione dati: pensiamo di utilizzare il modello HLT dell’upgrade di
LHCb (i.e. no L0)
Walter M. Bonivento - CERN/INFN Cagliari
!11
CNS2 18/02/2014
Il magnete (x2)
•
L’esperimento richiede un magnete dipolare simile a quello
di LHCb, ma con 40% meno ferro e tre volte meno
potenza dissipata.
!
•
2
LHCb: 4Tm e Apertura di ~ 16 m
!
•
Questo design:
!
2
- Apertura 20 m
- Due bobine di Al-99.7
- Campo di picco ~ 0.2 T
- Integrale di campo ~ 0.5 Tm su 5 m
!
•
risoluzione in massa 40MeV per p<20GeV (75% dei
decadimenti hanno entrambe le tracce che soddisfano a
questo criterio)
!
!
!
+ magnete per rivelatore di ντ (possibilmente ricuperato da
qualche magnete al CERN o altrove)
Walter M. Bonivento - CERN/INFN Cagliari
!12
CNS2 18/02/2014
Soppressione fondi
•
Interazioni di neutrini attivi
fondo
•
nel tunnel di decadimento: a pressione -5
4
atmosferica 2x10 interazioni —>vuoto 10 bar
-8
(molto meno di NA62 che usa 10 bar!)
•
nell’ultima lunghezza
di interazione del dump —0
>produzione di K L—>μπν
20
•
in 2x10
pot 600k CC interazioni di νμ
•
150 eventi con entrambe le particelle cariche
che escono dallo spettrometro —>rigettate
da tagli cinematica sul parametro di impatto
•
inoltre un altro fattore 10 si puo’ ottenere
istrumentando l’ultima parte del dump per
“taggare” le interazioni di neutrino
Walter M. Bonivento - CERN/INFN Cagliari
!13
segnale
CNS2 18/02/2014
Sensibilita’
•
Assumendo 0 fondo (che pare
ben giustificato dai nostri studi)!
•
finestra di opportunità’ per
questo esperimento di sondare
la zona di interesse cosmologico!
BBN
•
se si rinuncia a spiegare la Dark
Matter —>modello molto meno
vincolato, spazio dei parametri di
interesse cosmologico più esteso,
HNL non degeneri
Walter M. Bonivento - CERN/INFN Cagliari
!14
solo con N—>μπ
(in uno scenario in cui l’accoppiamento !
al sapore muonico e’ dominante)
CNS2 18/02/2014
Altre misure possibili
•
•
•
Studio delle interazioni del neutrino τ con statistica
150x attuale!
•
L’esperimento DONUT ha osservato 9 eventi (da
charm) con 1.5 stimato di fondo!
•
L’esperimento OPERA ha osservato 3 eventi (da
oscillazione)!
Rivelatore a emulsioni con la tecnologia di OPERA (De
Lellis) ma con massa molto minore (375 mattoni)
molto compatto (2m) posto davanti al tunnel di
decadimento per il HNL —>immerso in campo B
(consentirebbe l’dentificazione di anti-ντ, mai
osservati) e seguito da un rivelatore di muoni (per
sopprimere il fondo di charm)!
Si stima di dovere cambiare il rivelatore
circa 10 volte
2
nel corso del run —>totale di 2700 m di piates di
emulsioni —> 2.5% di OPERA
Walter M. Bonivento - CERN/INFN Cagliari
!15
Sensibilità’ da valutare per
particelle esotiche a vita media
lunga e interagenti molto
debolmente con massa leggera
(portali per l’Hidden sector)
CNS2 18/02/2014
Collaborazione
internazionale
Gruppo iniziale di poche persone:
CERN, I(Cagliari,Napoli), CH(Zurigo), UK (ICL): 4
spoke-persons nella collaborazione! + vari
teorici(EPFL,INR Moscow, ILTP Leiden)
!
!
Contatti avviati con molti altri gruppi in varie nazioni
Walter M. Bonivento - CERN/INFN Cagliari
!16
CNS2 18/02/2014
Opportunità per INFN
•
Siamo tra i proponenti e progettisti iniziali quindi partiamo con il piede
giusto!
•
•
In questa fase tutte le idee innovative e buone sono benaccette.
Al momento abbiamo la responsabilità’ di coordinare il sistema PID
(mu,CALO e veto calo) e co-coordinare il rivelatore di ντ (Giovanni de
Lellis, NA) ma altri si inseriranno rapidamente —>fare in fretta a
decidere cosa ci interessa costruire!
•
Rivelatori, meccanica, elettronica —>progettazione da fare
•
trigger, DAQ,computing: esperti del CERN coinvolti nel design; valutando le
soluzioni più innovative per il computing model: stiamo pensando a FairRoot
•
idee di fisica aggiuntive, simulazioni
Walter M. Bonivento - CERN/INFN Cagliari
!17
CNS2 18/02/2014
Stato della proposta (i)
•
SPC EOI-2013-010 + addendum sottomessa Ottobre 2013 e discussa alla
riunione. EOI trasmessa e discussa al Research Board ma non ancora
valutata da quest’ultimo.!
•
interazione con referee di SPSc e discussione alla riunione di Gennaio 2014. !
•
Raccomandazione SPSc:
The Committee received with interest the response of the proponents to the
questions raised in its review of EOI010.
The SPSC recognises the interesting physics potential of searching for
heavy neutral leptons and investigating the properties of neutrinos.
Considering the large cost and complexity of the required beam
infrastructure as well as the significant associated beam intensity, such
a project should be designed as a general purpose beam dump facility with
the broadest possible physics programme, including maximum reach in
the investigation of the hidden sector.
To further review the project the Committee would need an extended
proposal with further developed physics goals, a more detailed technical
design and a stronger collaboration.
Walter M. Bonivento - CERN/INFN Cagliari
!18
CNS2 18/02/2014
Stato della proposta (2)
•
L’Extended Directorat del CERN ha istituito (la settimana scorsa) una task force
composta da fisici degli acceleratori del CERN (e.g. Arduini) per dare un “first
assessment” per la fattibilita’ del nostro esperimento in termini di beam line e
dump!
1. dare un input alla discussione allo Scientific Policy Committee a Maggio !
2. la cui raccomandazione sara’ (probabilmente) trasferita al Council di Giugno!
•
Primo meeting open di Collaborazione il 10-12 Giugno (stiamo fissando il luogo,
vicino al CERN, Francia o Svizzera): sara’ un workshop a cui sono invitati molti
teorici e si discutera’ un progetto tecnico preliminare dell’esperimento!
•
Pagina web http://ship.web.cern.ch/ship/ !
•
Tempo stimato per il proposal: 1 anno.!
•
Costo stimato: 100M per il fascio 30M per il rivelatore (inclusi i contributi in-kind)
Walter M. Bonivento - CERN/INFN Cagliari
!19
CNS2 18/02/2014
Visti da fuori(1)
Final remarks
•
New physics can show up at low energy, in the form of low-mass
BSM particles (vMSM neutral leptons, sterile ν’s, axions, low-mass
WIMPS) or high-scale phenomena revealed by low-scale processes
(B, D decays/mixings, μ→eγ, g–2, EDM, etc)
•
None of these observations would reduce the interest in expanding
the energy reach of direct exploration
Ancora
First expressions of interest for
physics with the injectors
Mangano !
a
Workshop
del FCC !
• The direct understanding of the true nature of EWSBalremains
critical component of the programme (among many reasons, cfr e.g.
settimana scorsa a!
remarks on EW phase transition and baryogenesis, by Nima and la
Christophe)
an
• Naturalness remains an ever-growing concern, which cries forGinevra!!!!!
FHC.1.3 Continued exploration of SM particles
FHC.1.3.1 Physics of the top quark (rare decays, FCNC, anomalous couplings, ...)
FHC.1.3.2 Physics of the bottom quark (rare decays, CPV, ...)
FHC.1.3.2 Physics of the tau lepton (e.g. tau -> 3 mu, tau -> mu gamma and other LFV
decays)
FHC.1.3.2 W/Z physics
FHC.1.3.3 QCD dynamics
extension of the energy reach of our facilities
FHC.1.4 Opportunities other than pp physics:
FHC.1.4.1 Heavy Ion Collisions
FHC.1.4.2 Fixed target experiments:
FHC.1.4.2.1 "Intensity frontier": kaon physics, mu2e conversions, beam dump experiments
and searches for heavy photons, heavy neutrals, and other exotica...
FHC.1.4.2.2 Heavy Ion beams for fixed-target experiments
FHC.1.5 Theoretical tools for the study of 100 TeV collisions
Walter M. Bonivento - CERN/INFN Cagliari
FHC.1.5.1 PDFs!20
FHC.1.5.2 MC generators
CNS2 18/02/2014
Visti da fuori(2)
Is it the end?
Certainly not!
-- Dark matter
-- Baryon Asymmetry in Universe
-- Neutrino masses
are experimental proofs that there is more
to understand.
We must continue our quest
Alain Blondel FCC-ee experiments summary
at least 3 pieces are still missing
Blondel, plenary summary !
FCC-ee al Workshop !
della settimana scorsa a!
Ginevra!!!!!
Since 1998 it is established that neutrinos have mass
and this very probably implies new degrees of freedom
«sterile», very small coupling to known particles
completely unknown masses (eV to ZeV), nearly impossile to find.
.... but could
explain
all:summary
DM, BAU, -masses
Alainperhaps
Blondel FCC-ee
experiments
Walter M. Bonivento - CERN/INFN Cagliari
!21
CNS2 18/02/2014
Conclusioni
•
Test di una spiegazione alternativa rispetto ai soliti modelli (SUSY, ED) di
importanti fenomeni osservati non compatibili con il Modello Standard !
•
Tecniche complementari rispetto a esperimenti esistenti —>lunghe vite medie!
•
Anche fisica dei neutrini attivi, per gli appassionati
•
Il fascio c’e’ e il rivelatore si puo’ costruire in breve tempo appena data
l’approvazione. Tutte le tecnologie proposte esistono e funzionano! Non ci
sono R&D cruciali per l’esperimento che necessitano anni di studi preliminari.!
•
Una proposta che il CERN sta valutando molto seriamente. Nessuna altra
facility al mondo ha (e aggiungerei avra’, viste le proposte in circolazione) le
potenzialita’ per effettuare questa misura con sensibilita’ competitive o
comunque in grado di sondare la regione di interesse cosmologico, per m>mK!
•
Una grande opportunita’ per l’Ente di imbarcarsi su questa nave e decidere la
rotta! Chi e’ interessato si faccia avanti!!
Walter M. Bonivento - CERN/INFN Cagliari
!22
CNS2 18/02/2014
Dovevamo parlare di N1
•
Stabilita’ —> τ>τ(universo)!
•
Produzione —>creato
nell’Universo nella fase iniziale
nelle reazioni ll—>νN1 , qq—>νN1
deve fornire la corretta
abbondanza di DM!
•
Decadimento —> il decadimento
radiativo N1—>γν fornisce una
linea nello spettro X a E(γ)=m1/2!
•
Allargamento linea da Doppler e
da effetti strumentali vari!
!
Walter M. Bonivento - CERN/INFN Cagliari
zona di esclusione!
(OTTENUTA CON MISURE!
SU SINGOLE GALASSIE)
!23
CNS2 18/02/2014
!
!
!
Submitted to ApJ, 2014 February 10
Preprint typeset using LATEX style emulateapj v. 04/17/13
DETECTION OF AN UNIDENTIFIED EMISSION LINE IN THE STACKED X-RA
CLUSTERS
with heavy elements (Mitchell et al. (1976); Serlemitsos
now we do know for sure it exists — from X-ray and
et al. (1977) and later works) that escape from galaxies
Walter
M. Bonivento
- CERN/INFN Cagliari medium
CNS2
gravitational-lensing observations
of the18/02/2014
Bullet Cluster,
and accumulate
in the intracluster/intergalactic
!24 Clowe et al. (2006), and we know accurately its cosmo(ICM) over billions of years of galactic and stellar evo1
Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridg
NASA Goddard Space Flight Center, Greenbelt, MD, USA.
Submitted to ApJ, 2014 February 10
Esra Bulbul1,2 , Maxim Markevitch2 , Adam Foster1 , Randall K. Smith1 Mich
Scott W. Randall1
1. INTRODUCTION
states and nonthermal emission
processesdi
such as charge
la significanza
dichiarata e’ 3σ —>pertanto
e’
il
caso
exchange (Paerels & Kahn 2003).
Galaxy clusters are the largest aggregations of hot inAs for dark matter, 80 years from its discovery by
tergalactic
gas and dark
The cauti.
gas is enriched
aspettare
ed matter.
essere
(Zwicky 1933, 1937), its nature is still unknown (though
ABSTRACT
We detect a weak unidentified emission line at E = (3.55 3.57) ± 0.03 ke
spectrum of 73 galaxy clusters spanning a redshift range 0.01 0.35. MOS
independently show the presence of the line at consistent energies. When the
into three subsamples (Perseus, Centaurus+Ophiuchus+Coma, and all other
> 3 statistical significance in all three independent MOS spectra and the PN
The line is also detected at the same energy in the Chandra ACIS-S and ACIS-I
cluster, with a flux consistent with XMM-Newton (however, it is not seen in t
Virgo). The line is present even if we allow maximum freedom for all the kn
lines. However, it is very weak (with an equivalent width in the full sample of on
within 50–110 eV of several known faint lines; the detection is at the limit of
capabilities and subject to significant modeling uncertainties. On the origin of
there should be no atomic transitions in thermal plasma at this energy. An i
the decay of sterile neutrino, a long-sought dark matter particle candidate. A
matter is in sterile neutrinos with ms = 2E = 7.1 keV, our detection in the full
a neutrino decay mixing angle sin2 (2✓) ⇡ 7 ⇥ 10 11 , below the previous upper
on the cluster masses and distances, the line in Perseus is much brighter than e
significantly deviating from other subsamples. This appears to be because of
line at E = 3.62 keV in Perseus, which could be an Arxvii dielectronic recom
its emissivity would have to be 30 times the expected value and physically diffi
principle, such an anomaly might explain our line detection in other subsam
would stretch the line energy uncertainties. Another alternative is the above
combined with the nearby 3.51 keV K line also exceeding expectation by facto
with Chandra and Suzaku, and eventually Astro-H, are required to determine
line.
1. INTRODUCTION
states and nonthermal em
exchange (Paerels & Kah
As for dark matter, 8
(Zwicky 1933, 1937), its n
now we do know for sur
gravitational-lensing obse
Clowe et al. (2006), and
logical abundance, e.g., H
the various plausible dar
has motivated our presen
ile neutrino that is inclu
standard model of particl
(1994) and later works;
Abazajian et al. (2007);
ile neutrinos should decay
(ms , ✓) = 1.38 ⇥ 10
where the particle mass
are unknown but tied to
neutrino production mod
The decay of sterile neutr
E = ms /2 and an active
ile neutrino may lie in the
•
Galaxy clusters are the largest aggregations of hot intergalactic gas and dark matter. The gas is enriched
with heavy elements (Mitchell et al. (1976); Serlemitsos
et al. (1977) and later works) that escape from galaxies
and accumulate in the intracluster/intergalactic medium
(ICM) over billions of years of galactic and stellar evolution. The presence of various heavy ions is seen from
their emission lines in the cluster X-ray spectra. Data
from large e↵ective area telescopes with spectroscopic capabilities, such as ASCA, Chandra, XMM-Newton and
Suzaku, uncovered the presence of many elements in the
ICM, including O, Ne, Mg, Si, S, Ar, Ca, Fe, and Ni
(for a review see, e.g., B¨ohringer & Werner 2010). Recently, weak emission lines of low-abundance Cr and Mn
were discovered (Werner et al. 2006; Tamura et al. 2009).
Relative abundances of various elements contain valuable
information on the rate of supernovae of di↵erent types in
galaxies (e.g., Loewenstein 2013) and illuminate the enrichment history of the ICM (e.g., Bulbul et al. 2012b).
Line ratios of various ions can also provide diagnostics
of the physical properties of the ICM, uncover the presence of multi-temperature gas, nonequilibrium ionization
•
[email protected]
!
Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138.
2 NASA Goddard Space Flight Center, Greenbelt, MD, USA.
Submitted to ApJ, 2014 February 10
CNN breaking news
1
2
idea: mettere insieme 73 osservazioni di galassie per
aumentare la statistica: analizzate le osservazioni di XMMNewton e Chandra. Correzioni per il red-shift etc.
ABSTRACT
We detect a weak unidentified emission line at E = (3.55 3.57) ± 0.03 keV in a stacked XMM
spectrum of 73 galaxy clusters spanning a redshift range 0.01 0.35. MOS and PN observations
independently show the presence of the line at consistent energies. When the full sample is divided
into three subsamples (Perseus, Centaurus+Ophiuchus+Coma, and all others), the line is seen at
> 3 statistical significance in all three independent MOS spectra and the PN “all others” spectrum.
The line is also detected at the same energy in the Chandra ACIS-S and ACIS-I spectra of the Perseus
cluster, with a flux consistent with XMM-Newton (however, it is not seen in the ACIS-I spectrum of
Virgo). The line is present even if we allow maximum freedom for all the known thermal emission
lines. However, it is very weak (with an equivalent width in the full sample of only ⇠ 1 eV) and located
within 50–110 eV of several known faint lines;
the detection is at the
limit of the current
instrument
arXiv:1402.2301v1
[astro-ph.CO]
10 Feb
2014
capabilities and subject to significant modeling uncertainties. On the origin of this line, we argue that
there should be no atomic transitions in thermal plasma at this energy. An intriguing possibility is
the decay of sterile neutrino, a long-sought dark matter particle candidate. Assuming that all dark
matter is in sterile neutrinos with ms = 2E = 7.1 keV, our detection in the full sample corresponds to
a neutrino decay mixing angle sin2 (2✓) ⇡ 7 ⇥ 10 11 , below the previous upper limits. However, based
on the cluster masses and distances, the line in Perseus is much brighter than expected in this model,
significantly deviating from other subsamples. This appears to be because of an anomalously bright
line at E = 3.62 keV in Perseus, which could be an Arxvii dielectronic recombination line, although
its emissivity would have to be 30 times the expected value and physically difficult to understand. In
principle, such an anomaly might explain our line detection in other subsamples as well, though it
would stretch the line energy uncertainties. Another alternative is the above anomaly in the Ar line
combined with the nearby 3.51 keV K line also exceeding expectation by factor 10–20. Confirmation
with Chandra and Suzaku, and eventually Astro-H, are required to determine the nature of this new
line.
:1402.2301v1 [astro-ph.CO] 10 Feb 2014
DETECTION OF AN UNIDENTIFIED EMISSION LINE IN THE STACKED X-RAY SPECTRUM OF GALAXY
CLUSTERS
Esra Bulbul1,2 , Maxim Markevitch2 , Adam Foster1 , Randall K. Smith1 Michael Loewenstein2 , and
Scott W. Randall1
Un altra breaking news!
An unidentified line in X-ray spectra of the Andromeda galaxy and Perseus galaxy cluster
A. Boyarsky1 , O. Ruchayskiy2, D. Iakubovskyi3,4 and J. Franse1,5
Instituut-Lorentz for Theoretical Physics, Universiteit Leiden, Niels Bohrweg 2, Leiden, The Netherlands
2
Ecole Polytechnique F´ed´erale de Lausanne, FSB/ITP/LPPC, BSP, CH-1015, Lausanne, Switzerland
3
Bogolyubov Institute of Theoretical Physics, Metrologichna Str. 14-b, 03680, Kyiv, Ukraine
4
National University “Kyiv-Mohyla Academy”, Skovorody Str. 2, 04070, Kyiv, Ukraine
5
Leiden Observatory, Leiden University, Niels Bohrweg 2, Leiden, The Netherlands
We identify a weak line at E ∼ 3.5 keV in X-ray spectra of the Andromeda galaxy and the Perseus galaxy
cluster – two dark matter-dominated objects, for which there exist deep exposures with the XMM-Newton X-ray
observatory. Such a line was not previously known to be present in the spectra of galaxies or galaxy clusters.
Although the line is weak, it has a clear tendency to become stronger towards the centers of the objects; it is
stronger for the Perseus cluster than for the Andromeda galaxy and is absent in the spectrum of a very deep
“blank sky” dataset. Although for individual objects it is hard to exclude the possibility that the feature is due
to an instrumental effect or an atomic line of anomalous brightness, it is consistent with the behavior of a line
originating from the decay of dark matter particles. Future detections or non-detections of this line in multiple
astrophysical targets may help to reveal its nature.
arXiv:1402.4119v1 [astro-ph.CO] 17 Feb 2014
2
Ecole
Polytechnique
F´ed´erale de Lausanne, FS
3
Bogolyubov
Institute of Theoretical Physics
4
National University “Kyiv-Mohyla Acade
Leiden Observatory, Leiden University,
We identify a weak line at E ∼ 3.5 keV in X-ray
cluster – two dark matter-dominated objects, for which
observatory. Such a line was not previously known t
Although the line is weak, it has a clear tendency to
stronger for the Perseus cluster than for the Androm
“blank sky” dataset. Although for individual objects
to an instrumental effect or an atomic line of anomal
originating from the decay of dark matter particles. F
astrophysical targets may help to reveal its nature.
The nature of dark matter (DM) is a question of crucial importance for both cosmology and for fundamental physics. As
neutrinos – the only known particles that could be dark matter candidates – are known to be too light to be consistent with
various observations (see e.g. [1] for a review), it is widely anticipated that a new particle should exist to extend the hot Big
Bang cosmology paradigm to dark matter. Although many
candidates have been put forward by particle physicists (see
e.g. [2]), little is known experimentally about the properties
of DM particles: their masses, lifetimes, and interaction types
remain largely unconstrained. A priori, a given DM candidate
can possess a decay channel if its lifetime exceeds the age
of the Universe. Therefore, the search for a DM decay signal
provides an important test to constrain the properties of DM in
a model-independent way. For fermionic particles, one should
search above the Tremaine-Gunn limit [3] (! 300 eV). If the
mass is below 2me c2 , such a fermion can decay to neutrinos
and photons, and we can expect two-body radiative decay with
photon energy Eγ = 21 mDM . Such particles can be searched
for in X-rays (see [4] for review of previous searches). For
each particular DM model, the particle’s mass, lifetime and
other parameters are related by the requirement to provide the
correct DM abundance. For example, for one very interesting
DM candidate – the right-handed neutrino – this requirement
restricts the mass range to 0.5 − 100 keV [4, 5]. A large part
of the available parameter space for sterile neutrinos is fully
consistent with all astrophysical and cosmological bounds [6],
and it is important to probe it still further.
The DM decay line is much narrower than the spectral resolution of the present day X-ray telescopes and, as previous
searches have shown, should be rather weak. The X-ray spectra of astrophysical objects are crowded with weak atomic and
instrumental lines, not all of which may be known. Therefore,
even if the exposure of available observations continues to increase, it is hard to exclude an astrophysical or instrumental
origin of any weak line found in the spectrum of individual
The nature of darkconsistente
matter (DM) is a question
of crucial
object. However,
the same
feature is present in the spectra
• Osservazione
di una
lineaimat 3.5KeV
with if3-4
σ significance
portance for both cosmology and for fundamental physics. As
of a number of different objects, and its surface brightness and
neutrinos – the only known particles that could be dark matrelative normalization between objects is consistent with the
ter candidates
– are known
too light to be consistent
expected behavior
the DM signal,
this cansulle
provideshape
much
• Analisi
diversa
dallato be
precedente
e suwith
dati diversi,
con ofcontrolli
anche
ecc.
various observations (see e.g. [1] for a review), it is widely anmore convincing evidence about its nature.
ticipated that a new particle should exist to extend the hot Big
The present paper takes a step in this direction. We present
Bang analisi
cosmology paradigm
to dark
matter.
Although many
• Molte
in corso
che
potranno
chiarire
la situazione!
the results of the combined analysis of many XMM-Newton
candidates have been put forward by particle physicists (see
observations of two objects at different redshifts – the Perseus
e.g. [2]), little is known experimentally about the properties
and the Andromeda galaxy (M31) – together with a
of DM particles:
their masses,
lifetimes,
and interaction
• Missione
Astro-H
sara’
lanciata
neltypes
2015cluster
e
aiutera’
a chiarire la situazione
long exposure “blank sky” dataset. We study the 2.8–8 keV
remain largely unconstrained. A priori, a given DM candidate
energy band and show that the only significant un-modeled
can possess a decay channel if its lifetime exceeds the age
excess that is present in the spectra of both M31 and Perseus
of the Universe. Therefore, the search for a DM decay signal
is located at ∼ 3.5 keV energy and the lineCNS2
in Perseus
is corWalter
M.
Cagliari
18/02/2014
provides
anBonivento
important test-toCERN/INFN
constrain the properties
of DM in
2
!
5
rectly redshifted as compared to Andromeda (at 95% CL). The
a model-independent way. For fermionic particles, one should
5
.4119v1 [astro-ph.CO] 17 Feb 2014
1
Nel grafico bi-dimensionale
cases, such as the core of the Perseus cluster where many
neutral filaments are known, it is possible that CX could
-7
10be
large enough
to create a small fraction of the total
DM overproduction
X-ray emission, although Excluded
it would notbycreate
or enhance
X-ray
observations
-8
10a line at 3.57 keV or the DR line at 3.62 keV. CX could
not dominate the overall emission, however, as it would
-9 create Fe XVII and other lines that are not detected.
10also
10-10
Tremaine-Gunn / Lyman-α
2
Interaction strength Sin (2θ)
22
5.2. Sterile neutrino decay line?
An interesting interpretation of the line is the decay
signature of the sterile neutrino, a long-sought dark mat10-11
ter particle candidate (Boyarsky et al. (e.g., 2009), see
our §1). The mass of the sterile neutrino would be douNot
enough
DM m =7.1 keV. The line flux
10-12
ble the decay
photon
energy,
s
detected
in
our
full
sample
corresponds
to a mixing angle
-13
10 for the decay sin2 (2✓) ⇠ 7 ⇥ 10 11 . This value is below
1
2
5
10
50
the upper limits placed by the previous searches, shown
Dark matter
MDMXMM-Newton
[keV]
in Fig. 12. Our detection
from themass
stacked
MOS observations galaxy clusters are shown with a star
in red in that figure. Figure 13 shows the detections and
upper limits we obtained from our various subsamples we
FIG. 4:
Constraints
on(based
sterileonneutrino
DM cluster
withinmasses
νMSM [4]. The
used
in this work
the included
blue point
would corresponds
to the best-fit
from
and distances),
as well as a comparison
with value
previous
up- M31 if the
per limit
placed
the Thick
Bullet errorbars
cluster by are
Boyarsky
line comes
from
DMusing
decay.
±1σ et
limits on the
al. (2008) at 3.57 keV, which is the most relevant earlier
flux. Thin
errorbars
to the uncertainty
in the DM distri
Figure 12. Recent constraints on sterile neutrino production
constraint
for us.correspond
Since the mixing
angle is a universal
models, assuming sterile neutrinos constitute dark matter (Abazabutionquantity,
in the center
M31. measurements must agree.
all theofsubsample
jian et al. 2007). Straight lines in black show theoretical predictions
The line in the subsample of fainter 69 clusters (full
assuming sterile neutrinos constitute the dark matter with lepton
number L = 0, L = 0.003, L = 0.01, L = 0.1. Constraints from the
sample sans Perseus, Coma, Ophiuchus and Centaurus)
cosmic
X-rayM.
background
are -shown
in the solidCagliari
(blue and hatched
Walter
Bonivento
CERN/INFN
corresponds to a mixing angleCNS2
that is18/02/2014
consistent with
regions). The region is solid green is excluded based upon obser- !26
the full sample; the same is seen (though with a mild
vations of the di↵use X-ray background (Abazajian et al. 2007).
Boyarski et al.
Harvard, NASA ecc.
e’ un campo vivo,
vedremo…
Fine
Le camere
diChambers
tracciamento
Tracking
NA62 (K + → π + ν ν¯):
• 2 m ! vessel @0.01 µbar.
• 10 mm ! straws made of PET.
• Demonstrated to work in vacuum.
• X/X0=0.5 % for 4 view station!
• 120 µm resolution/straw.
H.Dijkstra
Nikhef 24/1/14
Walter M. Bonivento - CERN/INFN Cagliari
- 25 -
!29
CNS2 18/02/2014
Il calorimetro e il rivelatore di
muoni
Electromagnetic Calo
LHCb Shashlik ECAL:
• 6.3×7.8 m2
√
σ(E)
• E < 10%/ E ⊕ 1.5%
LHCb ECAL
Larger/better than required.
But for N → µρ(ππ 0 (γγ))
need small (10 × 10 cm2 ) cells everywhere.
H.Dijkstra
Nikhef 24/1/14
Walter M. Bonivento - CERN/INFN Cagliari
- 28 -
!30
CNS2 18/02/2014

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