Search for Excited Quarkby HERA e-p Collider

KUHEP colloquium22th Jun, 2009

Maeda Yosuke

22th Jun, 2009 KUHEP colloquiumSearch for Excited Quark by HERA ep Collider

2/total

contents

• HERA e-p collider

• physics in HERA collider

• compositeness model

• H1 detector

• analysis

• summary

HERA in myth

22th Jun, 2009 KUHEP colloquiumSearch for Excited Quark by HERA ep Collider

3/total

HERA e-p collider

• DESY in Hamburg, Germany• only e-p collider in the world• 27.6GeV e+/e-, 920(820)GeV p (√s = 319(301)GeV)• data taking

1992-2000(HERA-I) 2002-2007(HERA-II)

• integrated luminosity 475 pb-1

e-p : 184pb-1

e+p : 291pb-1

　 (35pb-1 with low energy)

(Hadron Elektron Ring Anlage)

Hamburg★

e+/e-

pHERA (6.4km)

PETRA

22th Jun, 2009 KUHEP colloquiumSearch for Excited Quark by HERA ep Collider

4/total

physics in HERA collider

• further search for internal structure with larger Q2

– Deep Inelastic Scattering (DIS)

• model-dependent new physics– leptoquark– excited fermions (leptons, quarks)– single top production

• comparison with SM– W production (We,)

– isolated event with missing PT

– multi-lepton final states

Q2 = -q2 = -(k-k’)2

(Q2 ~ 1/)

x = Q2/(2p ･ q)

y= 　 (p ･ q)/(p ･ k)

22th Jun, 2009 KUHEP colloquiumSearch for Excited Quark by HERA ep Collider

5/total

compositeness model

• Leptons and quarks are composite of more fundamental constituents.– explanation of 3 generations of quarks and leptons– excited fermions as a natural consequence of this model

• excited quarks– energy region : TeV, a few hundred GeV possible– interaction with ordinary fermions :

– : compositeness scalef, f’,fs : coupling parameter

– only right-handed doublet F*R is allowed

– In this analysis, assume f=f’, fs=0

SU(2) U(1) SU(3)C

22th Jun, 2009 KUHEP colloquiumSearch for Excited Quark by HERA ep Collider

6/total

H1 detector

• concept– accurate lepton identification– high granularity and resolution

for hadronic jet

• asymmetric design– CM = 2.86 (in p direction)

• inner tracker• EM / hadronic

calorimeter• detector

e+/e-

p

z

y

x

interacion point

22th Jun, 2009 KUHEP colloquiumSearch for Excited Quark by HERA ep Collider

7/total

inner tracking detectors

• measure momenta and angle of charged particle• provide fast trigger signal

• central part– acceptance : 15 - 165 deg– silicon tracker– MWPC (CIP, COP, CIZ, COZ)

r~170m, z~400m– jet type chamber(CJC1, CJC2)– (pT)/pT ~ 0.008pT[GeV]

• forward part– planar drift chambers, TRD, MWPC

pe+/e-

z

22th Jun, 2009 KUHEP colloquiumSearch for Excited Quark by HERA ep Collider

8/total

calorimeters

• Liquid Argon Calorimeters– acceptance : 4 - 154 deg– electromagnetic section

• (20-30)X0 with 2.4mm-thick lead

• EM(E)/E = 12%/√E[GeV] + 1%

– hadronic section• (5-8) with 19mm-thick stainless steal

• had(E)/E = 50%/√E[GeV] + 2%

– total 44354 channels

• SpaCal / sandwich (lead and scintillation fiber)– acceptance : 153 - 177.5 deg (measurement in the backward region)

– divided into EM section and hadronic section

1.15T magnetic field parallel to z axis by superconducting coil

5.75m

6m

SpaCalLAr calorimter

22th Jun, 2009 KUHEP colloquiumSearch for Excited Quark by HERA ep Collider

9/total

other detectors

• tail catcher– measure leak of hadronic shower

and penetrating – ten 7.5cm-thick iron layer and

16 layers of streamer tube– 5 - 15mm spatial resolution

• luminosity measurement– use Bethe-Heitler process of small angle bremsstrahlung

(The cross section is well calculated)– detectors : electron tagger (ET) @ z=-33.4m,

photon detector (PD) @ z=-102.9m(segmented crystal Cerenkov counter)

trackingSpaCal

FNC PLUGVLQ

z

e+/e-

p

22th Jun, 2009 KUHEP colloquiumSearch for Excited Quark by HERA ep Collider

10/total

photos of H1 detectors

LAr calorimeter

tracking chamber(CJC1, CJC2)

silicon tracker(FDT)

SpaCal

example of event display

22th Jun, 2009 KUHEP colloquiumSearch for Excited Quark by HERA ep Collider

11/total

analysis

• decay mode to search here :– q*q, q*qW/Zqqq, q*qWql, q*qZqll (l=e,)

• trigger : EM or hadronic energy deposit in LAr or missing transverse energy (rate : 10-20MHz)

• require reconstructed z vertex to be within 35cm from the nominal interaction point

• find e, , and hadron jet candidates– e, : compact and iolated shower in EM section of calorimeters

(further require small hadronic energy deposit, to be isolated from any other jet and association with inner tracks)

– m : inner track and signal in muon detectors(less than 5GeV deposit in a cylinder)

– hadron jet : energy deposit in calorimeters except above(associated with inner tracks)

22th Jun, 2009 KUHEP colloquiumSearch for Excited Quark by HERA ep Collider

12/total

search for q*q

• signal : one isolated EM cluster with high pT and one jet with high pT

• background : SM radiative NC DIS and prompt photon• cut condition

– 5 deg < < 90 deg, pT>35GeV

– 5 deg < jet < 80 deg, pTjet>20GeV

– Bjorken scaling value x=Q2/M>0.1(exclude photoproduction events)

– reject EM energy deposit of >10GeV in LAr(NC DIS rejection)

→44 events remained (SM prediction : 46 +/- 8 events)

22th Jun, 2009 KUHEP colloquiumSearch for Excited Quark by HERA ep Collider

13/total

search for q*qqq

• signal : 3 high pT jets (q*qWqqq, q*qZqqq)

• background : multi-jet photoproduction and NC DIS• cut condition

– at least 3 jets with 5 deg < jet < 120 deg

– pT >50GeV, 30GeV, 15GeV

– invariant mass of 2 jets with low pT

close to W or Z mass (70GeV~100GeV)

→341 events remained(SM prediction : 326 +/- 78 events)

22th Jun, 2009 KUHEP colloquiumSearch for Excited Quark by HERA ep Collider

14/total

search for q*qe, q• signal : 1 lepton, 1 jet and missing pT

• background : W production(SM DIS, photoproduction and lepton pair production can also be background by mismeasurement)

• cut condition () for q*q

– missing pT > 25GeV

– pTe,>10GeV, 5 deg < e, < 100 deg,

e cluster must be isolated from any other jetwith R>1 (R=√(2+2), : rapidity)

– for e, Vap/Va>0.25 (to reject photoproduction event)

– pTjet>20(15)GeV, 5 deg < jet < 100(160) deg

(pTjet>25GeV for jet<60deg in q*q)

– invariant mass of e(m) and missing 55GeV ~ 100GeV (for e), >40GeV (for )

q*q5 event(SM:4.4+/-0.7)

q*qe6 event(SM:6.0+/-0.8)

22th Jun, 2009 KUHEP colloquiumSearch for Excited Quark by HERA ep Collider

15/total

search for q*qee, q

• signal : 2 high pT leptons and 1 jet

• background : SM lepton pair creation• cut condition () for q*q

– 5 deg < e < 100(160) deg, pTe>20(15)GeV, 10GeV

– for e, associated good quality track in 5 deg < e < 35 deg

– invariant mass : MZ +/- 7GeV (for e), >50GeV (for )

– 5 deg < jet < 100 deg, pTjet>20GeV

→No data remained for both e and .(SM prediction : 0.44 +/- 0.08 for e, 0.87 +/- 0.11 for )

22th Jun, 2009 KUHEP colloquiumSearch for Excited Quark by HERA ep Collider

16/total

setting upper limits

• f=f’, fs=0– branching ratio of q*(95% C.L.)

– q* mass (assume f/ ~ 1/Mq*) exclude <252GeV

– limit on f/ exclude wider region than the result of DELPHI at LEP

• effect of non-zero fs

– large SM dijet background– Mq*<190– complement result with CDF

22th Jun, 2009 KUHEP colloquiumSearch for Excited Quark by HERA ep Collider

17/total

summary

• Excited quarks are searched for using the full data of e-p collision by H1 detector at HERA. (L=475fb-1)

• H1 is designed as a multi-purpose detector, and focused on good lepton identification and energy resolution by using LAr.

• The decay modes of excited quark q*q, q*qqq, q*ql, q*qll (=q,) are examined. Results are in good agreement with SM prediction, and there is no evidence of q* existence with the assumption of f=f’ and fs=0

• With the assumption above, Mq*<252GeV is excluded.