Long-lived Signature
Koichi Hamaguchi (Tokyo U.)@「LHCが切り拓く新しい物理」, Tokyo U., April ’09

based on.....S.Asai, KH, S.Shirai, arXiv:0902.3754

introduction

Long-lived particleの例（in SUSY)

赤・・・charged
青・・・missing

stau ➔ gravitino + tau (gravitino LSP)
stau ➔ neutralino + tau(質量縮退)

stau ➔ neutrino + tau (small R-parityviolation)stau(NLSP)~1/F ~ 1/MP
neutralino ➔ gravitino + photon (gravitinoLSP)
gravitino (LSP)
wino( ) ➔ wino(0) + pi( ) (anomaly mediation)
gluino ➔ neutralino + q, qbar

(split SUSY)Long-lived particleの例（in SUSY)

赤・・・charged
青・・・missing

stau ➔ gravitino + tau (gravitino LSP)
stau ➔ neutralino + tau(質量縮退)

stau ➔ neutrino + tau (small R-parity violation)neutralino ➔ gravitino + photon (gravitino LSP)
wino( ) ➔ wino(0) + pi( ) (anomaly mediation)
gluino ➔ neutralino + q, qbar

(split SUSY)

Gravitino
andNLSP at
the LHC!
G!
G!
GNLSP

NLSP

次の東さんのトーク

charged trackくんのトーク)“kink” incharged track寿命測れる？？

寿命測れる

寿命測れる？

( cf. 昨年の白井

τ! NLSPχ! NLSP 2γ + ET,miss0

今日はこれの話

non-pointingphoton
寿命測れる

the same asχ
!0 LSP signal....

何故 Long-lived charged particle(e.g. long-lived stau) を考えるのか？
理由１：long-lived stau は event としてはexotic だがモデルはそんなに exotic じゃない。
（聞く人にも依ると思いますが・・・。)

何故 Long-lived charged particle(e.g. long-lived stau) を考えるのか？
理由１：long-lived stau は event としてはexotic だがモデルはそんなに exotic じゃない。
（聞く人にも依ると思いますが・・・。)

理由２：もしあったら、寿命を測る事がとても大事だから。(SUSY breaking scale の測定、
もしかしたら Planck scale の測定も？！）（cf. 去年の私のトーク）rkameSi de R

Planck scale measurement
W.Buchmüller, K.Hamaguchi, M.Ratz, T.Yanagida ’04

rkameSi de R

Planck scale measurement
W.Buchmüller, K.Hamaguchi, M.Ratz, T.Yanagida ’04

何故 Long-lived charged particle(e.g. long-lived stau) を考えるのか？
理由１：long-lived stau は event としてはexotic だがモデルはそんなに exotic じゃない。
（聞く人にも依ると思いますが・・・。)

理由２：もしあったら、寿命を測る事がとても大事だから。(SUSY breaking scale の測定、
もしかしたら Planck scale の測定も？！）（cf. 去年の私のトーク）

理由３：cosmology (Li-7問題)

OKOK??

Fig. from Review of Particle Physics

recently, reanalyzed byCyburt, Fields, Olive, 0808.2818
OK

Abstract: “The Li problem
remains and indeed exacerbated;OKthe discrepancy is now 4.2σ - 5.3σ.”“Li-7 problem”??

観測Fig. from Review of Particle Physics

予言This Li-7 problem may be solved if there isa long-lived [O(1000 sec)] charged particle !
decay effect:(destroy Li-7)(not necessarily charged)
Jedmzik,’04;+ (many others)+ Cumberbatch, Ichikawa, Kawasaki,Kohri, Silk, Starkman,’07

catalysis effect:(7Be X-)+p → (8B X-)+Υ
Pospelov,’06;+ Bird, Koopmans, Pospelov,’07+ Kusakabe, Kajino, Boyd, Yoshida,Mathews,’07,+ Kamimura, Kino, Hiyama,’08(cf. Takayama,’08, Jedamzik,’08,Jittoh, Kohri, Koike, Sato, Shimomura,
Yamanaka’07’08)

Mission: Supposethat we will see
stopper-detector
KH, Kuno, Nakaya, Nojiri ’04
long-lived charged
massive
KH, Nojiri, DeRoeck’06 particle at the LHC,e.g., stau NLSP in SUSY models.
τ̃864
20-2-4-6-8-12-10-8-6-4

τ̃-2CMS02468

10120-2-4-6-8-10108642

If its lifetime is long (> 1 sec),
can we see its decay??
KH, Kuno, Nakaya, Nojiri,’04
Yes! with additional stoppers.

Feng, Smith,’04
KH, Nojiri, De Roeck,’06

Yes! without additional material. Asai, KH, Shirai,’09

this talk実は、去年の同じ研究会（08年3月）で「LSPがGravitinoになるモデルとLHCでの物理」というタイトルでお話して・・・

その時、Long-lived stau の話をして、最後のスライドで次のような質問をしました。質問！
中には detector 内で止まって、遅れて崩壊するやつも居るはずです。（beta < 0.4 くらい。遅すぎる？）

τ̃

τ

τ̃G̃

何とかしてこいつら identify 出来ないでしょうか？
(cf. Dimopoulos達の “stopping gluino” (at ATLAS) hep-ph/0506242)

今日はこの続きのお話をします。

Stop and Decay
ofLong-lived Charged Massive Particles
at the LHC detectors

S.Asai, KH, S.Shirai, arXiv:0902.3754

• typically most of staus have large
velocity and escape from detector.
• momentum measurement p• + TOF (time of flight) measurement T➩ velocity β = L/Tτ̃• mass m = p/(βγ) cf.cf. 昨日の河野さんのtalk
De Roeck, Ellis, Gianotti, Moortgat, Olive, Pape, 05∆mτemτe=∆pp⊕ βγ 2∆tL

O(1000) τ! →" 10 − 20%∆mτemτein each event< 1%• さらに他の粒子の質量（やスピンも?!）測れる(Hinchliffe,Paige,’98, Ambrosanio et.al.,’00, .....
..... Rajaraman,Smith 0708, Kitano 0801, 0806,.....)

• typically most of staus have large
velocity and escape from detector.

• some of them have sufficiently small
velocity and stop at calorimeters.

• typically most of staus have large
velocity and escape from detector.

• some of them have sufficiently small
velocity and stop at calorimeters.
thickness!± , χ!0 → τ!
typically g!, q! → χfor 100 GeV
stau(number of events)/bin/5fb-1

2000

1500

LHC

1000

500

0

βγ (= momentum／mass)

Fig. from
KH, Kuno,Nakaya,
Nojiri ’04
02

4

68

βγ (= momentum／mass)!"• typically most of staus have large
velocity and escape from detector.

• some of them have sufficiently small
velocity and stop at calorimeters.
example of SUSY
model point SPS7
( σSUSY = 3.5 pb )35000 SUSY
eventsfrom Asai, KH, Shirai ’09

Thickness: assume
Fe 1440mm (barrel)
Cu 1400mm (end-cap)

stopped events• about 1% oftotal SUSY events• a few per day(for 1033/cm^2 s)stau• but their late-time decay has wrong timing
and wrong direction;• difficult to reject backgrounds• difficult to trigger.

..... during pp collision.

pstaup• but their late-time decay has wrong timing
and wrong direction;• difficult to reject backgrounds• difficult to trigger.

..... during pp collision.

Idea:

stop the pp collision !!
....and optimize the trigger
to detect the stau decay(= isolated energetic cluster in HCAL)

two possible strategies:• for short lifetime: use beam-damp signal.
• for long lifetime: use shutdown time.

• for short lifetime:

use beam-damp signal.

(I) select the stopping event by online Event Filter.

SUSY stopped!!
eventstime• for short lifetime:

use beam-damp signal.

(I) select the stopping event by online Event Filter.
(1) missing ET > 100 GeV(2) 1 jet PT > 100 GeV + 2 jets PT > 50 GeV

standardSUSY cuts(3) isolated track with PT > 0.1 m(stau).

staucandidate(4) extrapolate the track to calorimeter andenergy deposit < 0.2 p(stau).
(5) extrapolate the track to muon system andno muon track.
SUSY stopped!!
eventsselectstopping
eventstime• for short lifetime:

use beam-damp signal.

(I) select the stopping event by online Event Filter.

SUSY stopped!!
eventstime• for short lifetime:

use beam-damp signal.

(I) select the stopping event by online Event Filter.
(II) send a beam-damp signal, which immediatelystops the pp collision.

triggerbeam-damp
SUSY stopped!!
eventstime• for short lifetime:

use beam-damp signal.

(I) select the stopping event by online Event Filter.
(II) send a beam-damp signal, which immediatelystops the pp collision.

trigger(III) change the trigger menu to the one optimized
for stau decay.

beam-damp
SUSY stopped!!
eventschangetrigger menutime• for short lifetime:

use beam-damp signal.

(I) select the stopping event by online Event Filter.
(II) send a beam-damp signal, which immediately
stops the pp collision.

trigger(III) change the trigger menu to the one optimized
for stau decay.
(IV) wait for stau decay.

beam-damp
SUSY stopped!!
eventschangetrigger menu
decay!!

Δttime• for short lifetime:

use beam-damp signal.

(I) select the stopping event by online Event Filter.
(II) send a beam-damp signal, which immediately
stops the pp collision.

trigger(III) change the trigger menu to the one optimized
for stau decay.
(IV) wait for stau decay.

beam-damp
SUSY stopped!!
eventsrestart pp collisionchangetrigger menu
decay!!

Δt

SUSY
eventstime• for long lifetime:running (pp collision)use shutdown time

winter shutdown

stoppedtime

• for long lifetime:use shutdown timerunning (pp collision)

winter shutdown

stoppedchangetrigger menu
decay!!

time•lifetime measurement: SUMMARY

shortassumption

dead time: 1 sec
waiting time: 30 min.
running: 200 days
shutdown: 100 days
longO(0.1 sec .... 100 years) can be probed!!

Summary
If we will see
long-lived charged massive particle at the LHC,the lifetime measurement is important both forcosmology and particle physics.
The discovery of late decay, and the lifetime
measurement is possible for a very wide range,from O(0.1 sec) to O(100 years) !!!
Future works:

study of decay products (energy? particle IDs?)
what about long-lived colored particle (R-hadrons) ?

Backup Slides

Catalyzed BBN (CBBN) Pospelov ’06
If there were negatively charged particle, X- at BBN,...
➔ bound states with positively charged nuclei.
➔ new catalyzed reactions occur!

(1) strong constraints (Li6) on X lifetime and abundance.
standard BBN

catalyzed BBN

O(109) enhancement !!!
➔ too much Li6 !!!
Pospelov ’06;.......; KH, Hatsuda, Kamimura, Kino, Yanagida ’07

Catalyzed BBN (CBBN) Pospelov ’06
If there were negatively charged particle, X- at BBN,...
➔ bound states with positively charged nuclei.
➔ new catalyzed reactions occur!

(1) strong constraints (Li6) on X lifetime and abundance.
(2) there may already exist a hint of this CBBN.
➔ Li7 problem.

Catalyzed BBN (CBBN) Pospelov ’06
If there were negatively charged particle, X- at BBN,...
➔ bound states with positively charged nuclei.
➔ new catalyzed reactions occur!

(1) strong constraints (Li6) on X lifetime and abundance.
..... if(2) there may already exist a hint of this CBBN.
X lifetime is➔ Li7 problem.
O(1000) sec.
CBBN can solve it!
(7Be X-)+p → (8B X-)+Υ
Pospelov,’06;☛ Such a long-lived charged particle+ Bird, Koopmans, Pospelov,’07
naturally arises in SUSY models with(+ many others)+ Kamimura, Kino, Hiyama,’08
gravitino LSP + stau NLSP!!

• What is Gravitino?

∪Super

1string

extremely weakly interacting• Why Gravitino LSP ?
• ..... among 29 SUSY particles?
squarks :!

"Lud"
L

#iu"
Rid"
Ri

"0 ,gauginos and higgssinos : χi%gravitino : G

sleptons :$χ±i ,g%!

ν"Le"
L

#ie"
Ri

• Why Gravitino LSP ?

Dark Matter in SUSYIn SUSY models + R-parity,
LSP (=Lightest SUSY Particle) is stable.

➞ If neutral, Dark Matter candidate!

• Why Gravitino LSP ?
Dark Matter candidates
in SUSY Standard Model
In SUSY Standard Model in SUGRA,.....
squarks :!

"Lud"
L

#iu"
Rid"
Ri"0 ,gauginos and higgssinos : χi%gravitino : Gsleptons :$χ±i ,g%!

ν"Le"
L

#ie"
Ri

excluded by direct
detection experiments(cf. Falk, Olive, Srednicki,’94)

neutral and color-singlet
Only Neutralino and Gravitino are viable candidates!

• まず、MSSM粒子＋gravitinoのうちDMになれるのはSUSY models

neutralino gravitino
LSPLSPothersfifty-fifty?

• Why Gravitino LSP ?

experimental boundnaturalness• Other SUSY particle masses = O(100 GeV)-O(1 TeV)
• Gravitino mass..... model dependent.
Gravitino masseVkeV

MeV

GeV

GMSB

TeV

̃gMSB

AMSB,mMSB

gravity-MSB

Gravitino LSPNLSP (Next-to-Lightest SUSY Particle)
In Gravitino LSP scenario, the NLSP is long-lived.

extremely weakinteraction

Lifetime e.g. for mNLSP ! 200 GeV
τNLSP ∼ O(day)for mGe ∼ 10 GeV

τNLSP ∼ O(10 min) for mGe ∼ 1 GeVτNLSP ∼ O(10 sec) for mGe ∼ 0.1 GeV• Why Stau NLSP ?
• ..... among 28 NLSP candidates?
squarks :!

"Lud"
L

#iu"
Rid"
Ri

"0 ,gauginos and higgssinos : χi%gravitino : G

sleptons :$χ±i ,g%

!

ν"Le"
L

#ie"
Ristau (i=3)

• Why Stau NLSP ?
• In general, from RGE, tendency is• M(color singlet) < M(colored)• M(weak singlet) < M(weak charged)• M(3rd family) < M(1st and 2nd family)

τ!1!!R!Re!R , µ!!

!

sleptons•typical RG evolution (from S.P.Martin, hep-ph/9709356)

ν"L""LgauginoHiggsino#gluinoq!

squarks

In most cases, either Stau or Neutralino is the NLSP

= Long-lived
charged particle.

SUSY models
neutralino
LSP

gravitino
LSPStau NLSP

Neutralino
NLSPothers• Gravitino LSP and Stau NLSP
is a natural choice.

NLSP Lifetime
Γ(τ̃ → G̃τ ) "m5τ̃2
48πm2G̃ Mpl

Lifetime of NLSP staumG̃

ττ̃

eV!

1−m2G̃
m2τ̃

"4e.g., for mτ̃ = 100 GeV ,MeVGeV

keV

particle physics の視点

psnsμsms . sec
からも寿命がとても大事

SUSY breaking√ scaleF =3 mGe MP

gravitino mass

mGe

day

O(1000) sec(Li7 problem)

NLSP Lifetime
Γ(τ̃ → G̃τ ) "m5τ̃
248πm2G̃ Mpl!

1−m2G̃
m2τ̃

"4Lifetime (decay length) of NLSP staumG̃eVττ̃cττ̃
promptdecaye.g., for mτ̃ = 100 GeV ,MeVGeV

keV
psns

μs

mmm

km

Detector
Size

mssec

day

O(1000) sec(Li7 problem)

No In-flight decay,
Target of this work!!

rkameSi de RPlanck scale measurement
W.Buchmüller, K.Hamaguchi, M.Ratz, T.Yanagida ’04